rocr: use driver interface for scratch memory deallocation

Replace direct hsaKmtFreeMemory call with driver's FreeMemory interface
in GpuAgent::ReleaseResources(). This change improves code abstraction
by handling memory deallocation through the unified driver interface.

Signed-off-by: Honglei Huang <Honglei1.Huang@amd.com>

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

@@ -929,7 +929,7 @@ void GpuAgent::ReleaseResources() {
     scratch_cache_.free_reserve();
 
     if (scratch_pool_.base() != NULL) {
-      HSAKMT_CALL(hsaKmtFreeMemory(scratch_pool_.base(), scratch_pool_.size()));
+      driver().FreeMemory(scratch_pool_.base(), scratch_pool_.size());
     }
 
     for (int i = 0; i < QueueCount; i++)