wsl/libhsakmt: fix return value for hsaKmtUnmapMemoryToGPU

Signed-off-by: Flora Cui <flora.cui@amd.com>
Reviewed-by: Tianci Yin <tianci.yin@amd.com>
Part-of: <http://10.67.69.192/wsl/rocr-runtime/-/merge_requests/89>

memory.cpp

@@ -845,6 +845,7 @@ HSAKMT_STATUS HSAKMTAPI hsaKmtUnmapMemoryToGPU(void *MemoryAddress) {
     }
   }
 
+  return HSAKMT_STATUS_SUCCESS;
 }
 
 HSAKMT_STATUS HSAKMTAPI hsaKmtMapGraphicHandle(HSAuint32 NodeId,