[IPV6] MIP6: Several obvious clean-ups.

- Remove redundant code.  Pointed out by Brian Haley <brian.haley@hp.com>.
- Unify code paths with/without CONFIG_IPV6_MIP.
- Use NIP6_FMT for IPv6 address textual presentation.
- Fold long line.  Pointed out by David Miller <davem@davemloft.net>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

net/ipv6/exthdrs.c

@@ -87,7 +87,6 @@ int ipv6_find_tlv(struct sk_buff *skb, int offset, int type)
 		len -= optlen;
 	}
 	/* not_found */
-	return -1;
  bad:
 	return -1;
 }