drm/amd/display: Add debug option to disable timing sync

[Why]
We want a debug option to disable timing sync for testing.

[How]
New dc debug option that must be false to call program_timing_sync

Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>