[OpenMP][libomptarget] Add hasQueue() function in NextGen plugin's AsyncInfoWrapperTy

[kevinsala]

Summary

This patch prepares the PluginInterface for the new AMDGPU NextGen plugin.

[jdoerfert]

LG, patches like this you can simply commit. Mark them as [NFC] also.

openmp/libomptarget/plugins-nextgen/common/PluginInterface/PluginInterface.h

struct AsyncInfoWrapperTy {
 
   /// Get a reference to the underlying plugin-specific queue type.
   template <typename Ty> Ty &getQueueAs() const {
     static_assert(sizeof(Ty) == sizeof(AsyncInfoPtr->Queue),
                   "Queue is not of the same size as target type");
     return reinterpret_cast<Ty &>(AsyncInfoPtr->Queue);
   }
 
+  /// Indicate whether there is queue.
+  bool hasQueue() const { return (AsyncInfoPtr->Queue != nullptr); }
+
 private:
   Error &Err;
   ErrorAsOutParameter ErrOutParam;
   GenericDeviceTy &Device;
   __tgt_async_info LocalAsyncInfo;
   __tgt_async_info *const AsyncInfoPtr;
 };