rfkill: remove input Kconfig

Now that we added the ioctl, there's no need to ask
the user to configure this. We will keep it enabled
for now, and eventually swap the default to n. Also
let embedded users select it only if they need it.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>