net/ipv6: Do not reset nl_net in ip6_route_info_create

nl_net is set on entry to ip6_route_info_create. Only devices
within that namespace are considered so no need to reset it
before returning.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>