[IPV6] XFRM: Fix auditing rt6i_flags; use RTF_xxx flags instead of RTCF_xxx.

RTCF_xxx flags, defined in include/linux/in_route.h) are available for
IPv4 route (rtable) entries only.  Use RTF_xxx flags instead, defined
in include/linux/ipv6_route.h, for IPv6 route entries (rt6_info).

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