display: Set default csc to BT709 + sRGB

- Initialize the color space of the SDM layer to BT709 +sRGB.
  Its the most generic csc + transfer, clients are free to override
  it to others.
- SetMetaData in gralloc with csc only for video buffers, this
  lets the UI buffers to be set to 709+sRGB

Change-Id: I3e7a3593d63cbbd7cdc65f0fcb49e0bcb66890ff
Crs-fixed: 2193203
3 files changed