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/device/rocm/rocsettings.cpp

@@ -86,6 +86,9 @@ Settings::Settings() {
 
   lcWavefrontSize64_ = true;
   imageBufferWar_ = false;
+
+  hmmFlags_ = (!flagIsDefault(ROC_HMM_FLAGS)) ? ROC_HMM_FLAGS :
+      Hmm::EnableSystemMemory | Hmm::EnableMallocPrefetch;
 }
 
 bool Settings::create(bool fullProfile, int gfxipMajor, int gfxipMinor, bool coop_groups) {