Allow both Wiener or sgrproj to be forced on
Allow both Wiener or sgrproj to be forced on

Minor refactoring to force only Wiener or Sgrproj to be
used for luma.

Change-Id: I81d6f5dbf0fbc07252b9c57b43a035b90c5699af

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