vxlan: Wrong type passed to %pIS

src_ip is a pointer to a union vxlan_addr, one member of which is a
struct sockaddr. Passing a pointer to src_ip is wrong; one should pass
the value of src_ip itself. Since %pIS formally expects something of
type struct sockaddr*, let's pass a pointer to the appropriate union
member, though this of course doesn't change the generated code.

Fixes: e4c7ed41 ("vxlan: add ipv6 support")
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>