drm/amd/display: Remove redundant check in atomic_check

[Why]
We have 2 back-to-back checks for skipping connectors.
Logically one of them will do the job.

[How]
Remove redundant check.

Reviewed-by: Hersen Wu <hersenxs.wu@amd.com&gt;>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>