hw/9pfs/virtio-9p-posix-acl: Fix out-of-bounds access

It's detected by coverity. Fix out-of-bounds access of the function mp_dacl_listxattr.
Signed-off-by: NShannon Zhao <zhaoshenglong@huawei.com>
Signed-off-by: NShannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

hw/9pfs/virtio-9p-posix-acl.c

@@ -114,7 +114,7 @@ static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path,
     }
 
     /* len includes the trailing NUL */
-    memcpy(value, ACL_ACCESS, len);
+    memcpy(value, ACL_DEFAULT, len);
     return 0;
 }