Use less tmp motion vectors in vp9_pick_inter_mode_sub8x8
Use less tmp motion vectors in vp9_pick_inter_mode_sub8x8

This commit simplifies the reference motion vector part for sub8x8
block coding in RTC mode and reduces the required local variables.

Change-Id: I470d1482092563b68af22404dc1f497e7457b0a8

stewnorriss/libvpx,zofuthan/libvpx,GrokImageCompression/aom,running770/libvpx,ittiamvpx/libvpx-1,felipebetancur/libvpx,pcwalton/libvpx,mwgoldsmith/vpx,GrokImageCompression/aom,ShiftMediaProject/libvpx,iniwf/webm.libvpx,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,pcwalton/libvpx,kim42083/webm.libvpx,Maria1099/webm.libvpx,jmvalin/aom,openpeer/libvpx_new,pcwalton/libvpx,charup/https---github.com-webmproject-libvpx-,pcwalton/libvpx,mbebenita/aom,goodleixiao/vpx,jacklicn/webm.libvpx,zofuthan/libvpx,lyx2014/libvpx_c,luctrudeau/aom,Distrotech/libvpx,shacklettbp/aom,shyamalschandra/libvpx,shareefalis/libvpx,mbebenita/aom,shyamalschandra/libvpx,Topopiccione/libvpx,VTCSecureLLC/libvpx,stewnorriss/libvpx,GrokImageCompression/aom,gshORTON/webm.libvpx,jmvalin/aom,smarter/aom,liqianggao/libvpx,ittiamvpx/libvpx-1,jacklicn/webm.libvpx,openpeer/libvpx_new,GrokImageCompression/aom,smarter/aom,mwgoldsmith/vpx,Topopiccione/libvpx,gshORTON/webm.libvpx,goodleixiao/vpx,iniwf/webm.libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,running770/libvpx,Acidburn0zzz/webm.libvpx,kim42083/webm.libvpx,mbebenita/aom,smarter/aom,goodleixiao/vpx,charup/https---github.com-webmproject-libvpx-,ShiftMediaProject/libvpx,Maria1099/webm.libvpx,mbebenita/aom,stewnorriss/libvpx,kleopatra999/webm.libvpx,jacklicn/webm.libvpx,Acidburn0zzz/webm.libvpx,zofuthan/libvpx,liqianggao/libvpx,GrokImageCompression/aom,running770/libvpx,shareefalis/libvpx,mwgoldsmith/vpx,thdav/aom,reimaginemedia/webm.libvpx,charup/https---github.com-webmproject-libvpx-,kleopatra999/webm.libvpx,altogother/webm.libvpx,zofuthan/libvpx,mwgoldsmith/libvpx,abwiz0086/webm.libvpx,jmvalin/aom,Distrotech/libvpx,goodleixiao/vpx,Distrotech/libvpx,luctrudeau/aom,running770/libvpx,luctrudeau/aom,Acidburn0zzz/webm.libvpx,kim42083/webm.libvpx,thdav/aom,webmproject/libvpx,altogother/webm.libvpx,Suvarna1488/webm.libvpx,hsueceumd/test_hui,Maria1099/webm.libvpx,stewnorriss/libvpx,jdm/libvpx,liqianggao/libvpx,Topopiccione/libvpx,kalli123/webm.libvpx,iniwf/webm.libvpx,Topopiccione/libvpx,reimaginemedia/webm.libvpx,zofuthan/libvpx,ShiftMediaProject/libvpx,charup/https---github.com-webmproject-libvpx-,gshORTON/webm.libvpx,felipebetancur/libvpx,liqianggao/libvpx,thdav/aom,kalli123/webm.libvpx,jdm/libvpx,ittiamvpx/libvpx-1,VTCSecureLLC/libvpx,kalli123/webm.libvpx,openpeer/libvpx_new,reimaginemedia/webm.libvpx,lyx2014/libvpx_c,ittiamvpx/libvpx-1,luctrudeau/aom,thdav/aom,mwgoldsmith/libvpx,VTCSecureLLC/libvpx,mbebenita/aom,running770/libvpx,abwiz0086/webm.libvpx,Distrotech/libvpx,openpeer/libvpx_new,Topopiccione/libvpx,ittiamvpx/libvpx-1,jdm/libvpx,matanbs/webm.libvpx,lyx2014/libvpx_c,hsueceumd/test_hui,webmproject/libvpx,abwiz0086/webm.libvpx,kalli123/webm.libvpx,smarter/aom,hsueceumd/test_hui,pcwalton/libvpx,zofuthan/libvpx,lyx2014/libvpx_c,jdm/libvpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,Distrotech/libvpx,shyamalschandra/libvpx,altogother/webm.libvpx,jmvalin/aom,shareefalis/libvpx,kleopatra999/webm.libvpx,iniwf/webm.libvpx,jmvalin/aom,Distrotech/libvpx,felipebetancur/libvpx,shacklettbp/aom,felipebetancur/libvpx,kalli123/webm.libvpx,lyx2014/libvpx_c,mbebenita/aom,kim42083/webm.libvpx,reimaginemedia/webm.libvpx,smarter/aom,altogother/webm.libvpx,shacklettbp/aom,stewnorriss/libvpx,shacklettbp/aom,iniwf/webm.libvpx,mbebenita/aom,matanbs/webm.libvpx,charup/https---github.com-webmproject-libvpx-,jmvalin/aom,abwiz0086/webm.libvpx,mwgoldsmith/libvpx,thdav/aom,smarter/aom,mwgoldsmith/libvpx,reimaginemedia/webm.libvpx,Maria1099/webm.libvpx,Suvarna1488/webm.libvpx,matanbs/webm.libvpx,Acidburn0zzz/webm.libvpx,mwgoldsmith/vpx,matanbs/webm.libvpx,altogother/webm.libvpx,Maria1099/webm.libvpx,gshORTON/webm.libvpx,liqianggao/libvpx,kleopatra999/webm.libvpx,jacklicn/webm.libvpx,hsueceumd/test_hui,jdm/libvpx,matanbs/webm.libvpx,ShiftMediaProject/libvpx,pcwalton/libvpx,jacklicn/webm.libvpx,thdav/aom,shareefalis/libvpx,Maria1099/webm.libvpx,abwiz0086/webm.libvpx,mbebenita/aom,kim42083/webm.libvpx,abwiz0086/webm.libvpx,shyamalschandra/libvpx,felipebetancur/libvpx,shyamalschandra/libvpx,Topopiccione/libvpx,reimaginemedia/webm.libvpx,mwgoldsmith/libvpx,mbebenita/aom,Suvarna1488/webm.libvpx,webmproject/libvpx,liqianggao/libvpx,openpeer/libvpx_new,Acidburn0zzz/webm.libvpx,VTCSecureLLC/libvpx,jdm/libvpx,Suvarna1488/webm.libvpx,goodleixiao/vpx,Suvarna1488/webm.libvpx,mwgoldsmith/vpx,luctrudeau/aom,luctrudeau/aom,kleopatra999/webm.libvpx,shacklettbp/aom,GrokImageCompression/aom,shacklettbp/aom,Suvarna1488/webm.libvpx,shareefalis/libvpx,webmproject/libvpx,matanbs/webm.libvpx,VTCSecureLLC/libvpx,shareefalis/libvpx,kalli123/webm.libvpx,hsueceumd/test_hui,kleopatra999/webm.libvpx,goodleixiao/vpx,hsueceumd/test_hui,gshORTON/webm.libvpx,running770/libvpx,Acidburn0zzz/webm.libvpx,jacklicn/webm.libvpx,openpeer/libvpx_new,shyamalschandra/libvpx,webmproject/libvpx,altogother/webm.libvpx,gshORTON/webm.libvpx,stewnorriss/libvpx,lyx2014/libvpx_c,iniwf/webm.libvpx,kim42083/webm.libvpx,charup/https---github.com-webmproject-libvpx-,webmproject/libvpx