mac80211: add back channel change flag

commit 24398e39
Author: Johannes Berg <johannes.berg@intel.com>
Date:   Wed Mar 28 10:58:36 2012 +0200

    mac80211: set HT channel before association

removed IEEE80211_CONF_CHANGE_CHANNEL argument from ieee80211_hw_config,
which is required by iwl4965 driver, otherwise that driver does not
configure channel properly and is not able to associate.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>