bonding: change some __constant_htons() to htons()

Resending since I didn't see any responses from the first try.

Change __constant_htons() to htons() in the bonding driver, it should
only be used for initializers.

-Brian

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>