[Kernel] Implement SetThreadPriority

src/core/kernel/kernel.cpp

@@ -25,6 +25,7 @@ void Kernel::serviceSVC(u32 svc) {
 		case 0x08: createThread(); break;
 		case 0x0A: svcSleepThread(); break;
 		case 0x0B: getThreadPriority(); break;
+		case 0x0C: setThreadPriority(); break;
 		case 0x13: createMutex(); break;
 		case 0x14: releaseMutex(); break;
 		case 0x17: createEvent(); break;