staging: brcm80211: fix for fullmac build problem

Fullmac had a build error for CONFIG_PM_SLEEP=n

Reviewed-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>