drm/amd/pp: Add powergate_gfx backend function on Raven

Raven support gfx off feature instand of gfx powergate,
so use smu10_gfx_off_control as the powergate_gfx backend function.
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c

@@ -1186,6 +1186,7 @@ static const struct pp_hwmgr_func smu10_hwmgr_funcs = {
 	.smus_notify_pwe = smu10_smus_notify_pwe,
 	.gfx_off_control = smu10_gfx_off_control,
 	.display_clock_voltage_request = smu10_display_clock_voltage_request,
+	.powergate_gfx = smu10_gfx_off_control,
 };
 
 int smu10_init_function_pointers(struct pp_hwmgr *hwmgr)