drm/amd/display: Fix bug that causes black screen

Ignore MSA bit on DP display is usually set during SetTimings, but
there was a case where the module thought refresh rate was not valid
and ignore MSA bit was not set.

Later, a valid refresh rate range was requested but since ignore MSA bit
not set, it caused black screen.

Issue if with how the module checked for VRR support. Fix up that logic.
DM should call new valid_range function to determine if timing is supported.

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>