net: fix warning in af_unix

This fixes the "'hash' may be used uninitialized in this function"

net/unix/af_unix.c:1041:20: warning: 'hash' may be used uninitialized in this function [-Wmaybe-uninitialized]
  addr->hash = hash ^ sk->sk_type;

Signed-off-by: Kyeongdon Kim <kyeongdon.kim@lge.com>
Signed-off-by: David S. Miller <davem@davemloft.net>