kernel/svc: Correct behavior of svcResetSignal()

While partially correct, this service call allows the retrieved event to
be null, as it also uses the same handle to check if it was referring to
a Process instance. The previous two changes put the necessary machinery
in place to allow for this, so we can simply call those member functions
here and be done with it.

src/core/hle/kernel/svc.cpp

@@ -1433,17 +1433,24 @@ static ResultCode CloseHandle(Handle handle) {
     return handle_table.Close(handle);
 }
 
-/// Reset an event
+/// Clears the signaled state of an event or process.
 static ResultCode ResetSignal(Handle handle) {
     LOG_DEBUG(Kernel_SVC, "called handle 0x{:08X}", handle);
 
     const auto& handle_table = Core::CurrentProcess()->GetHandleTable();
+
     auto event = handle_table.Get<ReadableEvent>(handle);
+    if (event) {
+        return event->Reset();
+    }
 
-    ASSERT(event != nullptr);
+    auto process = handle_table.Get<Process>(handle);
+    if (process) {
+        return process->ClearSignalState();
+    }
 
-    event->Clear();
-    return RESULT_SUCCESS;
+    LOG_ERROR(Kernel_SVC, "Invalid handle (0x{:08X})", handle);
+    return ERR_INVALID_HANDLE;
 }
 
 /// Creates a TransferMemory object