drm/amd/display: Consult MCCS FreeSync cap only if requested & supported

drm/amd/display: Consult MCCS FreeSync cap only if requested & supported

When the do_mccs parameter is false, we don't call
dm_helpers_read_mccs_caps, so sink->mccs_caps.freesync_supported is
unlikely to be true.

Fixes: 6f71d5dd3206 ("drm/amd/display: Read sink freesync support via mccs")
Bug: https://gitlab.freedesktop.org/drm/amd/-/work_items/5286
Signed-off-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ac3aea794fb4156467b4b3b92c3155d95bf435c9)
Cc: stable@vger.kernel.org