drm/radeon/atpx: check for ATIF dGPU wake for display events support

Some ATPX laptops implement special circuitry to generate
display hotplug events via ACPI when the dGPU is powered off.
Check if this is supported.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_atpx_handler.c

@@ -29,6 +29,7 @@ struct radeon_atpx {
 	acpi_handle handle;
 	struct radeon_atpx_functions functions;
 	bool is_hybrid;
+	bool dgpu_req_power_for_displays;
 };
 
 static struct radeon_atpx_priv {
@@ -72,6 +73,10 @@ bool radeon_is_atpx_hybrid(void) {
 	return radeon_atpx_priv.atpx.is_hybrid;
 }
 
+bool radeon_atpx_dgpu_req_power_for_displays(void) {
+	return radeon_atpx_priv.atpx.dgpu_req_power_for_displays;
+}
+
 /**
  * radeon_atpx_call - call an ATPX method
  *