Rework inter mode context for global_mv mode
Rework inter mode context for global_mv mode

Compare the motion filed reference motion vector with the global
mv to decide the context model for the compound inter mode coding.

Change-Id: I5606ba7571a19fc6577d1d65448f7052780f0c68

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom