net: ipv6: fix build failure if IPV6_ROUTE_INFO config is enabled

net: ipv6: fix build failure if IPV6_ROUTE_INFO config is enabled

Pass correct arguments to rt6_get_route_info() function, otherwise
we run into following Kernel build failure:
----------
  CC      net/ipv6/route.o
net/ipv6/route.c: In function ‘rt6_route_rcv’:
net/ipv6/route.c:746:27: error: ‘net’ undeclared (first use in this function)
net/ipv6/route.c:746:27: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [net/ipv6/route.o] Error 1
make[1]: *** [net/ipv6] Error 2
make: *** [net] Error 2
----------

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>