drm/amd/display: Add left edge pixel for YCbCr422/420 + ODM pipe split

[Why]
Currently 3-tap chroma subsampling is used for YCbCr422/420. When ODM
pipesplit is used, pixels on the left edge of ODM slices need one extra
pixel from the right edge of the previous slice to calculate the correct
chroma value.

Without this change, the chroma value is slightly different than
expected. This is usually imperceptible visually, but it impacts test
pattern CRCs for compliance test automation.

[How]
Update logic to use the register for adding extra left edge pixel for
YCbCr422/420 ODM cases.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>