[IPv6] rules: Remove bogus tos validation check

Noticed by Al Viro:
     (frh->tos & ~IPV6_FLOWINFO_MASK))
where IPV6_FLOWINFO_MASK is htonl(0xfffffff) and frh->tos
is u8, which makes no sense here...

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>