vpxenc: relocate vp8/vp9 only options
vpxenc: relocate vp8/vp9 only options

move them under their respective config check to avoid some unused
variable warnings when disabled

Change-Id: Ic5e5280cf1bc1f56e8349676f0bedae4acef34ea

mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,shyamalschandra/libvpx,zofuthan/libvpx,mbebenita/aom,liqianggao/libvpx,GrokImageCompression/aom,zofuthan/libvpx,shyamalschandra/libvpx,goodleixiao/vpx,openpeer/libvpx_new,shyamalschandra/libvpx,jmvalin/aom,mwgoldsmith/vpx,jmvalin/aom,thdav/aom,ittiamvpx/libvpx-1,jmvalin/aom,running770/libvpx,ShiftMediaProject/libvpx,smarter/aom,shacklettbp/aom,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,luctrudeau/aom,goodleixiao/vpx,stewnorriss/libvpx,felipebetancur/libvpx,webmproject/libvpx,GrokImageCompression/aom,stewnorriss/libvpx,smarter/aom,thdav/aom,GrokImageCompression/aom,shyamalschandra/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,Topopiccione/libvpx,mbebenita/aom,felipebetancur/libvpx,openpeer/libvpx_new,GrokImageCompression/aom,shacklettbp/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,thdav/aom,felipebetancur/libvpx,stewnorriss/libvpx,liqianggao/libvpx,luctrudeau/aom,zofuthan/libvpx,liqianggao/libvpx,ShiftMediaProject/libvpx,shacklettbp/aom,thdav/aom,thdav/aom,mbebenita/aom,webmproject/libvpx,jmvalin/aom,mwgoldsmith/vpx,openpeer/libvpx_new,smarter/aom,stewnorriss/libvpx,webmproject/libvpx,ittiamvpx/libvpx-1,running770/libvpx,shacklettbp/aom,VTCSecureLLC/libvpx,goodleixiao/vpx,running770/libvpx,luctrudeau/aom,liqianggao/libvpx,stewnorriss/libvpx,shacklettbp/aom,ittiamvpx/libvpx-1,mbebenita/aom,mwgoldsmith/vpx,VTCSecureLLC/libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,Topopiccione/libvpx,webmproject/libvpx,openpeer/libvpx_new,liqianggao/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,goodleixiao/vpx,luctrudeau/aom,running770/libvpx,VTCSecureLLC/libvpx,Topopiccione/libvpx,running770/libvpx,Topopiccione/libvpx,mbebenita/aom,stewnorriss/libvpx,openpeer/libvpx_new,felipebetancur/libvpx,shacklettbp/aom,goodleixiao/vpx,zofuthan/libvpx,jmvalin/aom,openpeer/libvpx_new,mwgoldsmith/libvpx,mwgoldsmith/vpx,smarter/aom,jmvalin/aom,ShiftMediaProject/libvpx,VTCSecureLLC/libvpx,VTCSecureLLC/libvpx,mwgoldsmith/vpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,running770/libvpx,thdav/aom,felipebetancur/libvpx,GrokImageCompression/aom,ittiamvpx/libvpx-1,liqianggao/libvpx,mbebenita/aom,webmproject/libvpx,shyamalschandra/libvpx,mbebenita/aom,webmproject/libvpx,Topopiccione/libvpx,zofuthan/libvpx,smarter/aom,smarter/aom,zofuthan/libvpx,Topopiccione/libvpx,goodleixiao/vpx,shyamalschandra/libvpx,mwgoldsmith/libvpx