rt2x00: bss_info_changed() callback is allowed to sleep

The bss_info_changed() callback function no longer needs
to be atomic. Remove the scheduled work structure and
call into the driver directly.

Additionaly this makes the DRIVER_REQUIRE_SCHEDULED
flag redundant so it can be removed.

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