gralloc: Remove localized hw specific pixel format

Reduces need to build with drm_gralloc headers elsewhere in tree.
Returning to system/graphics.h approach.

Change-Id: I26717cfe0a9a83ab263c26803e2849eb55560696
Depends-Change-Id: I405398b172fab19949fef33c89a60132b1bd0ea9
Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
2 files changed