mac80211: Checking IBSS support while changing channel in ad-hoc mode

This patch adds a check to the set_channel flow. When attempting to change
the channel while in IBSS mode, and the new channel does not support IBSS
mode, the flow return with an error value with no consequences on the
mac80211 and driver state.

Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211_i.h

@@ -899,7 +899,7 @@ extern const struct iw_handler_def ieee80211_iw_handler_def;
 
 
 /* ieee80211_ioctl.c */
-int ieee80211_set_freq(struct ieee80211_local *local, int freq);
+int ieee80211_set_freq(struct net_device *dev, int freq);
 /* ieee80211_sta.c */
 void ieee80211_sta_timer(unsigned long data);
 void ieee80211_sta_work(struct work_struct *work);