drm/amd/display: Block subvp if center timing is in use

drm/amd/display: Block subvp if center timing is in use

[Description]
- FW scheduling algorithm doesn't take into account of it's
  a center timing
- This affects where the subvp mclk switch can be scheduled
  (prevents HUBP vline interrupt from coming in if scheduled
  incorrectly)
- Block subvp center timing cases for now

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>