[OpenMP][NFC] Eliminate sign comparison warning via explicit casts

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D96812

Author: jdoerfert

openmp/libomptarget/plugins/cuda/src/rtl.cpp

@@ -229,7 +229,7 @@ class StreamManagerTy {
     const std::lock_guard<std::mutex> Lock(*StreamMtx[DeviceId]);
     int &Id = NextStreamId[DeviceId];
     // No CUstream left in the pool, we need to request from CUDA RT
-    if (Id == StreamPool[DeviceId].size()) {
+    if (Id == static_cast<int>(StreamPool[DeviceId].size())) {
       // By default we double the stream pool every time
       resizeStreamPool(DeviceId, Id * 2);
     }
@@ -263,7 +263,7 @@ class StreamManagerTy {
     resizeStreamPool(DeviceId, EnvNumInitialStreams);
 
     // Check the size of stream pool
-    if (StreamPool[DeviceId].size() != EnvNumInitialStreams)
+    if (static_cast<int>(StreamPool[DeviceId].size()) != EnvNumInitialStreams)
       return false;
 
     // Check whether each stream is valid