drm/amd/display: Stop storing failures into adev->dm.cached_state

drm/amd/display: Stop storing failures into adev->dm.cached_state

If drm_atomic_helper_suspend() has failed for any reason, it's stored
in adev->dm.cached_state.  This isn't expected because the resume
(or complete()) sequence will attempt to use the stored state to
resume.

Reviewed-by: Alex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250602014432.3538345-3-superm1@kernel.org
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>