drm/amdgpu/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 <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 void amdgpu_unregister_atpx_handler(void);
 bool amdgpu_has_atpx_dgpu_power_cntl(void);
 bool amdgpu_is_atpx_hybrid(void);
+bool amdgpu_atpx_dgpu_req_power_for_displays(void);
 #else
 static inline void amdgpu_register_atpx_handler(void) {}
 static inline void amdgpu_unregister_atpx_handler(void) {}
 static inline bool amdgpu_has_atpx_dgpu_power_cntl(void) { return false; }
 static inline bool amdgpu_is_atpx_hybrid(void) { return false; }
+static inline bool amdgpu_atpx_dgpu_req_power_for_displays(void) { return false; }
 #endif
 
 /*

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

···
 	acpi_handle handle;
 	struct amdgpu_atpx_functions functions;
 	bool is_hybrid;
+	bool dgpu_req_power_for_displays;
 };
 
 static struct amdgpu_atpx_priv {
···
 
 bool amdgpu_is_atpx_hybrid(void) {
 	return amdgpu_atpx_priv.atpx.is_hybrid;
+}
+
+bool amdgpu_atpx_dgpu_req_power_for_displays(void) {
+	return amdgpu_atpx_priv.atpx.dgpu_req_power_for_displays;
 }
 
 /**
···
 #endif
 		atpx->is_hybrid = true;
 	}
+
+	atpx->dgpu_req_power_for_displays = false;
+	if (valid_bits & ATPX_DGPU_REQ_POWER_FOR_DISPLAYS)
+		atpx->dgpu_req_power_for_displays = true;
 
 	return 0;
 }