Clean up convolve.c
Clean up convolve.c

Remove code related to convolve_round experiment out of
av1_convolve()

The experimental code is now implemented in av1_convolve_2d().

Change-Id: I409a390876e9d19e6ee42150f0ac20ff108244a9

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