vxlan: fix incorrect initializer in union vxlan_addr

The first initializer in the following

        union vxlan_addr ipa = {
            .sin.sin_addr.s_addr = tip,
            .sa.sa_family = AF_INET,
        };

is optimised away by the compiler, due to the second initializer,
therefore initialising .sin.sin_addr.s_addr always to 0.
This results in netlink messages indicating a L3 miss never contain the
missed IP address. This was observed with GCC 4.8 and 4.9. I do not know about previous versions.
The problem affects user space programs relying on an IP address being
sent as part of a netlink message indicating a L3 miss.

Changing
            .sa.sa_family = AF_INET,
to
            .sin.sin_family = AF_INET,
fixes the problem.

Signed-off-by: Gerhard Stenzel <gerhard.stenzel@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>