rt2x00: Cleanup rt2x00mac_bss_info_changed()

Since patch "rt2x00: bss_info_changed() callback is allowed to sleep" the
variable delayed wasn't used anymore. This means it can be removed
along with the call to schedule_work which depended on that variable.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>