drm/amd/display: Allow DSC on supported MST branch devices

drm/amd/display: Allow DSC on supported MST branch devices

commit 67d720c71dd52814aec725ae7ca2b3897e35645a upstream.

[Why]
When trying to lightup two 4k60 non-DSC displays behind a branch device
that supports DSC we can't lightup both at once due to bandwidth
limitations - each requires 48 VCPI slots but we only have 63.

[How]
The workaround already exists in the code but is guarded by a CONFIG
that cannot be set by the user and shouldn't need to be.

Check for specific branch device IDs to device whether to enable
the workaround for multiple display scenarios.

Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>