bonding: alb: convert to bond->mode_lock

The ALB/TLB specific spinlocks are no longer necessary as we now have
bond->mode_lock for this purpose, so convert them and remove them from
struct alb_bond_info.
Also remove the unneeded lock/unlock functions and use spin_lock/unlock
directly.

Suggested-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>