uapi: Add COLOR_FMT_NV12_512

HEIF HW encoding requires frames to be divided in 512x512 tiles.
Input frames, having width and height not a multiple of 512,
must be aligned to 512. Existing formats can't be modified to
accommodate HEIF's requirement because it will increase memory
footprint for all usecases of the modified color format.

Change-Id: I0dda7336bb98f04ebedb503598fa61044b8f8368
Signed-off-by: Amit Shekhar <ashekhar@codeaurora.org>
Signed-off-by: Sanjay Singh <c_sisanj@codeaurora.org>