drm/amd/display: ASSERT on dc_create_state failing.

dc_create_state() returns NULL on allocation failure. Raise warning when
that happens.
Signed-off-by: NLeo (Sunpeng) Li <sunpeng.li@amd.com>
Reviewed-by: NHarry Wentland <Harry.Wentland@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -702,6 +702,7 @@ int amdgpu_dm_display_resume(struct amdgpu_device *adev)
 	dc_release_state(cached_state->context);
 
 	cached_state->context = dc_create_state();
+	ASSERT(cached_state->context);
 	dc_resource_state_copy_construct_current(adev->dm.dc, cached_state->context);
 
 	for_each_new_crtc_in_state(adev->dm.cached_state, crtc, new_crtc_state, i) {