drm/amd/display: Fix ODM combine data format

[Why]
OPTC data format was left at its default value (444) when enabling
ODM combine. This caused issues with FPGA capture.

[How]
Write the OPTC_DATA_FORMAT field when enabling ODM combine.

Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Reviewed-by: Eric Bernstein <Eric.Bernstein@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Acked-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>