drm/amd/display: Fix timing not changning when freesync video is enabled

[Why&How]
Switching between certain modes that are freesync video modes and those
are not freesync video modes result in timing not changing as seen by
the monitor due to incorrect timing being driven.

The issue is fixed by ensuring that when a non freesync video mode is
set, we reset the freesync status on the crtc.

Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Alan Liu <HaoPing.Liu@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>