ath9k: remove incompatible IBSS interface check in change_iface

'cfg80211: fix interface combinations' ensures that if an interface
type is not advertised by the driver in any of the interface combinations
(via ieee80211_iface_combination) then it shall be treated as a single
incompatible interface. if there are more than one interfaces present
and changing them to incompatible interface type is not possible.
These checks will be properly handled by cfg80211_change_iface ->
cfg80211_can_change_interface.

this patch is dependent on 'cfg80211: fix interface combinations'

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -1467,15 +1467,6 @@ static int ath9k_change_interface(struct ieee80211_hw *hw,
 	mutex_lock(&sc->mutex);
 	ath9k_ps_wakeup(sc);
 
-	/* See if new interface type is valid. */
-	if ((new_type == NL80211_IFTYPE_ADHOC) &&
-	    (sc->nvifs > 1)) {
-		ath_err(common, "When using ADHOC, it must be the only"
-			" interface.\n");
-		ret = -EINVAL;
-		goto out;
-	}
-
 	if (ath9k_uses_beacons(new_type) &&
 	    !ath9k_uses_beacons(vif->type)) {
 		if (sc->nbcnvifs >= ATH_BCBUF) {