rocr: Return err when freeing invalid pointer

Return false if trying to free a NULL pointer (or invalid size)
internally in ROCr. This is to detect errors within ROCr when trying
to free NULL pointers. If a user of ROCr tries to free a NULL
pointer, this condition should be caught at the beginning of the
Runtime::FreeMemory(...) function and return HSA_STATUS_SUCCESS. This
matches the behavior of the free(...) or delete functions that
silently ignores calls when the passed a NULL pointer.

Change-Id: I84bc26928b35023e19cd9f214b42c6ee9508029c

runtime/hsa-runtime/core/driver/kfd/amd_kfd_driver.cpp

@@ -259,7 +259,7 @@ void *KfdDriver::AllocateKfdMemory(const HsaMemFlags &flags, uint32_t node_id,
 bool KfdDriver::FreeKfdMemory(void *mem, size_t size) {
   if (mem == nullptr || size == 0) {
     debug_print("Invalid free ptr:%p size:%lu\n", mem, size);
-    return true;
+    return false;
   }
 
   if (hsaKmtFreeMemory(mem, size) != HSAKMT_STATUS_SUCCESS) {