rt2x00: Detect initial rfkill state on register

When registering rfkill, make sure a initial
poll event is directly executed to detect the initial
rfkill state and send the event to the rfkill layer.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>