drm/amdgpu/acpi: skip backlight events for DC

No change in behavior, just bail sooner.
Reviewed-by: Jim Qu <Jim.Qu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c

@@ -389,7 +389,9 @@ static int amdgpu_atif_handler(struct amdgpu_device *adev,
 
 		DRM_DEBUG_DRIVER("ATIF: %d pending SBIOS requests\n", count);
 
-		if (req.pending & ATIF_PANEL_BRIGHTNESS_CHANGE_REQUEST) {
+		/* todo: add DC handling */
+		if ((req.pending & ATIF_PANEL_BRIGHTNESS_CHANGE_REQUEST) &&
+		    !amdgpu_device_has_dc_support(adev)) {
 			struct amdgpu_encoder *enc = atif->encoder_for_bl;
 
 			if (enc) {