rt2x00: Revert "rt2x00: Fix the beacon length bug"

This reverts:
	b93ce437
	rt2x00: Fix the beacon length bug

The workaround is no longer required since it has been
correctly fixed in rt2x00usb now.

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