Fix build errors:  add depends on NET.

ERROR: "skb_clone" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "dev_get_by_name" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "dev_remove_pack" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "init_net" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "__alloc_skb" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "kfree_skb" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "dev_add_pack" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "consume_skb" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "dev_queue_xmit" [drivers/staging/ozwpan/ozwpan.ko] undefined!
ERROR: "skb_put" [drivers/staging/ozwpan/ozwpan.ko] undefined!
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Chris Kelly <ckelly@ozmodevices.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>