rt2x00: Remove input_polldev requirements for rfkill

With the new rfkill interface there is no longer a need
for the input_polldev. Create a delayed_work structure
which we can put on the mac80211 workqueue and poll the
hardware every 1000ms.

v2: Decrease poll frequency from 100ms to 1000ms

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