radeon: add Mullins chip family

Signed-off-by: Samuel Li <samuel.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

radeon/radeon_surface.c

@@ -80,6 +80,7 @@ enum radeon_family {
     CHIP_KAVERI,
     CHIP_KABINI,
     CHIP_HAWAII,
+    CHIP_MULLINS,
     CHIP_LAST,
 };