[SYCL][NFC] Fix unused parameter warning in piQueueFlush

sycl/plugins/cuda/pi_cuda.cpp

@@ -2257,7 +2257,10 @@ pi_result cuda_piQueueFinish(pi_queue command_queue) {
 // There is no CUDA counterpart for queue flushing and we don't run into the
 // same problem of having to flush cross-queue dependencies as some of the
 // other plugins, so it can be left as no-op.
-pi_result cuda_piQueueFlush(pi_queue command_queue) { return PI_SUCCESS; }
+pi_result cuda_piQueueFlush(pi_queue command_queue) {
+  (void)command_queue;
+  return PI_SUCCESS;
+}
 
 /// Gets the native CUDA handle of a PI queue object
 ///

sycl/plugins/hip/pi_hip.cpp

@@ -2205,7 +2205,10 @@ pi_result hip_piQueueFinish(pi_queue command_queue) {
 // There is no HIP counterpart for queue flushing and we don't run into the
 // same problem of having to flush cross-queue dependencies as some of the
 // other plugins, so it can be left as no-op.
-pi_result hip_piQueueFlush(pi_queue command_queue) { return PI_SUCCESS; }
+pi_result hip_piQueueFlush(pi_queue command_queue) {
+  (void)command_queue;
+  return PI_SUCCESS;
+}
 
 /// Gets the native HIP handle of a PI queue object
 ///

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -3031,7 +3031,10 @@ pi_result piQueueFinish(pi_queue Queue) {
 
 // Flushing cross-queue dependencies is covered by createAndRetainPiZeEventList,
 // so this can be left as a no-op.
-pi_result piQueueFlush(pi_queue Queue) { return PI_SUCCESS; }
+pi_result piQueueFlush(pi_queue Queue) {
+  (void)Queue;
+  return PI_SUCCESS;
+}
 
 pi_result piextQueueGetNativeHandle(pi_queue Queue,
                                     pi_native_handle *NativeHandle) {