ipv6: routing header fixes

This patch fixes two bugs:

1. setsockopt() of anything but a Type 2 routing header should return
EINVAL instead of EPERM.  Noticed by Shan Wei
(shanwei@cn.fujitsu.com).

2. setsockopt()/sendmsg() of a Type 2 routing header with invalid
length or segments should return EINVAL.  These values are statically
fixed in RFC 3775, unlike the variable Type 0 was.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>