b43/b43legacy: add RFKILL_STATE_HARD_BLOCKED support

This patch sets the rfkill state to RFKILL_STATE_HARD_BLOCKED when the
radio is killed by the hardware switch.

Signed-off-by: Adel Gadllah <adel.gadllah@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>