mac80211: IBSS fix scan request

In case of wide bandwidth (wider than 20MHz) used by IBSS,
scan all channels in chandef to be able to find neighboring
IBSS netwqworks that use the same overall channels but a different
control channel.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>