VP9: Eliminate extra mv clamp in decoder
VP9: Eliminate extra mv clamp in decoder

The mv is clamped in dec_find_mv_refs() to a smaller region
than the clamp in dec_find_best_ref_mvs().  See clamp_mv_ref
and clamp_mv2.

Change-Id: I47dd5f7fa8b42f2cc593559b4d7c782fe7bcb1db

mwgoldsmith/libvpx,Topopiccione/libvpx,luctrudeau/aom,mwgoldsmith/vpx,mwgoldsmith/vpx,smarter/aom,webmproject/libvpx,Topopiccione/libvpx,webmproject/libvpx,mbebenita/aom,mbebenita/aom,ShiftMediaProject/libvpx,ittiamvpx/libvpx-1,smarter/aom,smarter/aom,ShiftMediaProject/libvpx,luctrudeau/aom,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,Topopiccione/libvpx,luctrudeau/aom,GrokImageCompression/aom,mwgoldsmith/vpx,Topopiccione/libvpx,GrokImageCompression/aom,mwgoldsmith/libvpx,mbebenita/aom,mwgoldsmith/libvpx,ittiamvpx/libvpx-1,mwgoldsmith/vpx,webmproject/libvpx,smarter/aom,GrokImageCompression/aom,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,mbebenita/aom,smarter/aom,Topopiccione/libvpx,webmproject/libvpx,Topopiccione/libvpx,luctrudeau/aom,mwgoldsmith/libvpx,ittiamvpx/libvpx-1,GrokImageCompression/aom,mbebenita/aom,webmproject/libvpx,mbebenita/aom,smarter/aom,mbebenita/aom,ittiamvpx/libvpx-1,mbebenita/aom,ShiftMediaProject/libvpx,mbebenita/aom,luctrudeau/aom,webmproject/libvpx,mwgoldsmith/libvpx,luctrudeau/aom,GrokImageCompression/aom,ittiamvpx/libvpx-1,GrokImageCompression/aom,ittiamvpx/libvpx-1