drm/amd/display: Add FAMS validation before trying to use it

To ensure that FAMS can be used, DC must check if there is VRR support.
This commit adds the required configuration to ensure FAMS can be executed in the target system.

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>