qemu: improve hugepage allocation failure message

Improve hugepage allocation failure message, indicating
what is happening to the user.
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

Message-Id: <20180115201700.GA4439@amt.cnet>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

numa.c

@@ -463,6 +463,7 @@ static void allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
             if (mem_prealloc) {
                 exit(1);
             }
+            error_report("falling back to regular RAM allocation.");
 
             /* Legacy behavior: if allocation failed, fall back to
              * regular RAM allocation.