drm/amd/display: fix exit from amdgpu_dm_atomic_check() abruptly

make action upon failure in "drm_atomic_add_affected_connectors()"
consistent with the rest of failures in amdgpu_dm_atomic_check().

Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>