When we have an active scheduled scan, and the RFKILL
interrupt kicks in, the stack will cancel the scheduled
scan as part of the down flow. But cancelling scheduled
scan usually implies sending a command to the firwmare
which has been killed as part of the RFKILL interrupt
handling.
Because of that, we returned an error to mac80211 when
it asked to stop the scheduled scan and didn't notify the
end of the scheduled scan. Besides a fat warning, this led
to a situation in which cfg80211 would refuse any new scan
request.

To disentangle this, fake that the scheduled scan has been
stopped without sending the command to the firwmare, return
0 after having properly let cfg80211 know that the scan
has been cancelled.

This is basically the same as:
commit 9b520d84
Author: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Date:   Tue Nov 4 15:54:11 2014 +0200

    iwlwifi: mvm: abort scan upon RFKILL

    This code existed but not for all the different FW APIs
    we support.
    Fix this.

but for the scheduled scan case.

Link: http://permalink.gmane.org/gmane.linux.kernel.wireless.general/133232Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>