Do not strip colorspace attribute for RGB888 surfaces.

Bug: 76088973
Test: Ran an internal test app that draws a solid bar of 50% gray and
1-pixel stripes alternating between black and white to a RGB888 surface.
Verified that the display matches expectations (the stripes and the bar
are approximately the same brightness).

Change-Id: I8682dfcaecf1034d74532b051bdd528b2e5e2870