[IPV4]: ip_route_input() annotations

ip_route_input() takes net-endian source and destination address.
* Annotated as such.
* arguments of its invocations annotated where needed.
* local helpers getting the same values passed to by it (ip_route_input_mc(),
ip_route_input_slow(), ip_handle_martian_source(), ip_mkroute_input(),
ip_mkroute_input_def(), __mkroute_input()) annotated

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>