Do not report reserved scratch cache as available

Scratch cache reserved memory is only available for scratch memory use
so do not report this memory as available to the user via the
HSA_AMD_AGENT_INFO_MEMORY_AVAIL api.

Change-Id: I52f96e62536458bcaa52b9f4be5de856d5680dc4


[ROCm/ROCR-Runtime commit: 3477fbc661]

projects/rocr-runtime/runtime/hsa-runtime/core/inc/scratch_cache.h

@@ -195,6 +195,7 @@ class ScratchCache {
   }
 
   size_t free_bytes() const { return available_bytes_; }
+  size_t reserved_bytes() const { return reserved_.first; }
 
   void reserve(size_t bytes, void* base) {
     assert(!reserved_.first && "Already reserved memory.");