Organize the model-rd functions into fn pointers
Organize the model-rd functions into fn pointers

Also includes a few misc. changes.

Change-Id: I4daf74bf88c243bcd6a18ec4d0b2d7f07aa62e7b

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