drm/amd/display: Add regamma/degamma coefficients and set sRGB when TF is BT709

drm/amd/display: Add regamma/degamma coefficients and set sRGB when TF is BT709

[Why]
In YUV case, need to set the input TF to sRGB instead of BT709,
even though the input TF type is distributed. SRGB was not
being used because pixel format was not being set in the
surface update sequence.
Also, we were using the same coefficients for degamma and
regamma formula, causing the cutoff point of the linear
section of the curve to be incorrect.

[How]
Set pixel format in the surface update sequence. Add separate
coefficient arrays for regamma and degamma.

Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Jaehyun Chung <jaehyun.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>