mac80211: return if IBSS chandef can not be used
mac80211: return if IBSS chandef can not be used

This was originally designed to fail when a 40+/40- mode can not be
used, but basic modes (such as 5/10/20 MHz) must be handled
with an error.

Signed-off-by: Simon Wunderlich <ee8cb2fe367357431f9fb32cc761adf92c257cce@hrz.tu-chemnitz.de>
Signed-off-by: Johannes Berg <8398eb9892c5ab2ff439ca0b5e4b0706dd9ebef9@sipsolutions.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs