[PATCH] bcm43xx: fix race condition in periodic work handler

There is a potential race condition in the periodic_work_handler routine
of bcm43xx-softmac. In addition to fixing this condition, the size of code is
reduced by moving the mutex lock outside the if.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>