9pfs: replace g_malloc()+memcpy() with g_memdup()

I found these pattern via grepping the source tree. I don't have a
coccinelle script for it!

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

hw/9pfs/9p-synth.c

@@ -494,8 +494,7 @@ static int synth_name_to_path(FsContext *ctx, V9fsPath *dir_path,
     }
 out:
     /* Copy the node pointer to fid */
-    target->data = g_malloc(sizeof(void *));
+    target->data = g_memdup(&node, sizeof(void *));
-    memcpy(target->data, &node, sizeof(void *));
     target->size = sizeof(void *);
     return 0;
 }