Initial HMM support

- Expose ROCclr interfaces for HIP usage
- ROCr interfaces aren't available in staging, thus control the
build with AMD_HMM_SUPPORT define

Change-Id: Iadc2bcc230e78d3b0dc22b235189c8cc80843446

rocclr/platform/command.cpp

@@ -203,7 +203,6 @@ bool Event::awaitCompletion() {
         lock_.wait();
       }
     }
-
     ClPrint(LOG_DEBUG, LOG_WAIT, "event %p wait completed", this);
   }
 
@@ -633,4 +632,13 @@ bool CopyMemoryP2PCommand::validateMemory() {
   return true;
 }
 
+// ================================================================================================
+bool SvmPrefetchAsyncCommand::validateMemory() {
+  amd::Memory* svmMem = svmMem = amd::MemObjMap::FindMemObj(dev_ptr());
+  if (nullptr == svmMem) {
+    LogPrintfError("SvmPrefetchAsync received unknown memory for prefetch: %p!", dev_ptr());
+    return false;
+  }
+}
+
 }  // namespace amd