b43: Fix typo in function name

This fixes a typo in the "b43_lo_g_maintenance_work" function
name.

Signed-off-by: Nik Nyby <nikolas@gnu.org>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Michael Buesch <m@bues.ch>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>