drm/amd/display: Query GECC enable for SubVP disable

drm/amd/display: Query GECC enable for SubVP disable

- We want to disable SubVP if Graphics Error Correction/Correcting Code
  (GECC) is enabled.
- After reading feature caps from DMCUB during init, use the GECC
  enable/disable info to determine if SubVP can be enabled or not.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>