[IPV4] fib_trie: build fix

Need this to fix build of fib_trie in net-2.6.16 (rebased) tree.
The code needs the new inet_make_mask inline.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>