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

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.");

runtime/hsa-runtime/core/runtime/amd_gpu_agent.cpp

@@ -1231,7 +1231,7 @@ hsa_status_t GpuAgent::GetInfo(hsa_agent_info_t attribute, void* value) const {
 
       for (auto r : regions()) availableBytes += ((AMD::MemoryRegion*)r)->GetCacheSize();
 
-      availableBytes += scratch_cache_.free_bytes();
+      availableBytes += scratch_cache_.free_bytes() - scratch_cache_.reserved_bytes();
 
       *((uint64_t*)value) = availableBytes;
       break;