[RFKILL]: Make state sysfs writable

The rfkill state Sysfs attribute should be made writable,
we already pass the argument for the store handler,
so we only need to update the permissions flag.

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