[IPV6] NDISC: Fix thinko to control Router Preference support.

Bug reported by Haruhito Watanabe <haruhito@sfc.keio.ac.jp>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed