gralloc: Use only metadata for color space

Currently both handle metadata and handle flags are used to indicate
the color space. This change deprecates support for flags.

Also gralloc doesn't set a color space based on use case anymore,
since front-end requirements keep changing. The default is set to 601
and the onus of correctly specifying the color space now rests on
clients.

CRs-fixed: 919117

Change-Id: I4988830e22804517b393c60dbe641d3bd1d790ec
2 files changed