vxlan: fix indentation

Some lines in vxlan code are indented by 7 spaces instead of a tab.

Fixes: e4c7ed41 ("vxlan: add ipv6 support")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>