[Palette] Fix partial colormap memcpy
[Palette] Fix partial colormap memcpy

Colormap memcpy must copy the entire colormap not just the visible
pixels

Change-Id: Ia2d5ab8684227f4f263b8396cf432c27c328bb47

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