[GSP::GPU] Implement writeHwRegs

include/services/gsp_gpu.hpp

@@ -15,6 +15,7 @@ class GPUService {
 	// Service commands
 	void acquireRight(u32 messagePointer);
 	void registerInterruptRelayQueue(u32 messagePointer);
+	void writeHwRegs(u32 messagePointer);
 
 public:
 	GPUService(Memory& mem, u32& currentPID) : mem(mem), currentPID(currentPID) {}