vxlan: Use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...))
trivial patch converting ERR_PTR(PTR_ERR()) into ERR_CAST().
No functional changes.
Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>