Revise precision clamping in GM param refinement
Revise precision clamping in GM param refinement

This ensures that the parameter refinement never
results in a motion parameter value that exceeds the number
of alloted bits in the bitstream. It accounts for all of
the necessary precision shifts required to make global motion compatible
with the warped motion library. It also accounts for the
zero-centering that is applied to global motion parameters that are
naturally centered around one.
Change-Id: If429c93bb90b66fdff0edc07ecd9fc078077d303

luctrudeau/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,smarter/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom