By default, disable mwaitx feature.

This can be enabled by setting HSA_ENABLE_MWAITX=1

Change-Id: I4be00892780beeb8b14c3c5f34aa10b158921bff

runtime/hsa-runtime/core/util/flag.h

@@ -164,7 +164,7 @@ class Flag {
     image_print_srd_ = (var == "1") ? true : false;
 
     var = os::GetEnvVar("HSA_ENABLE_MWAITX");
-    enable_mwaitx_ = (var == "0") ? false : true;
+    enable_mwaitx_ = (var == "1") ? true : false;
 
     // Temporary environment variable to disable CPU affinity override
     // Will either rename to HSA_OVERRIDE_CPU_AFFINITY later or remove completely.