bonding: fix enslaving in alb mode when link down

bond_alb_init_slave() is called from bond_enslave() and sets the slave's MAC
address. This is done differently for TLB and ALB modes.
bond->alb_info.rlb_enabled is used to discriminate between the two modes but
this flag may be uninitialized if the slave is being enslaved prior to calling
bond_open() -> bond_alb_initialize() on the master.

It turns out all the callers of alb_set_slave_mac_addr() pass
bond->alb_info.rlb_enabled as the hw parameter.

This patch cleans up the unnecessary parameter of alb_set_slave_mac_addr() and
makes the function decide based on the bonding mode instead, which fixes the
above problem.

Reported-by: Narendra K <Narendra_K@Dell.com>
Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>