bonding: fix alb mode locking regression

Fix locking issue in alb MAC address management; removed
incorrect locking and replaced with correct locking.  This bug was
introduced in commit 059fe7a578fba5bbb0fdc0365bfcf6218fa25eb0
("bonding: Convert locks to _bh, rework alb locking for new locking")

	Bug reported by Paul Smith <paul@mad-scientist.net>, who also
tested the fix.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>