bonding: Remove redundant argument from bond_create.

While we're fixing the bond_create, I hope it's OK to polish it
a bit after the fixes.

The third argument is NULL at the first caller and is ignored by
the second one, so remove it.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>