rocr: Make Open() and Close() virtual in Driver

Change-Id: Iac054c08383b080ca2b2ec6d65019bf2f083b763


[ROCm/ROCR-Runtime commit: 77fa5af618]

projects/rocr-runtime/runtime/hsa-runtime/core/runtime/amd_topology.cpp

@@ -458,9 +458,6 @@ bool Unload() {
 
   hsaKmtReleaseSystemProperties();
 
-  // Close connection to kernel driver.
-  hsaKmtCloseKFD();
-
   return true;
 }
 }  // namespace amd