drm/radeon: add get_allowed_info_register for SI

Registers that can be fetched from the info ioctl.

Tested-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/sid.h b/drivers/gpu/drm/radeon/sid.h
index 99a9835..3afac30 100644
--- a/drivers/gpu/drm/radeon/sid.h
+++ b/drivers/gpu/drm/radeon/sid.h
@@ -1556,6 +1556,7 @@
 #define UVD_UDEC_DBW_ADDR_CONFIG			0xEF54
 #define UVD_RBC_RB_RPTR					0xF690
 #define UVD_RBC_RB_WPTR					0xF694
+#define UVD_STATUS					0xf6bc
 
 #define	UVD_CGC_CTRL					0xF4B0
 #	define DCM					(1 << 0)