rfkill: allow toggling soft state in sysfs again

Apparently there actually _are_ tools that try to set
this in sysfs even though it wasn't supposed to be used
this way without claiming first. Guess what: now that
I've cleaned it all up it doesn't matter and we can
simply allow setting the soft-block state in sysfs.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Tested-By: Darren Salt <linux@youmustbejoking.demon.co.uk>
Signed-off-by: John W. Linville <linville@tuxdriver.com>