mac80211: remove WARN_ON() from ieee80211_hw_config

ieee80211_hw_config can return an error when the hardware
has rfkill enabled. A WARN_ON() is too harsh for this
failure as it is a valid scenario. Only comment this warning
as we would like to have it back when rfkill is integrated into
mac80211.

Also reintroduce propagation of error if ieee80211_hw_config fails
in ieee80211_config_beacon.

This patch partially reverts patch:
5f0387fc3337ca26f0745f945f550f0c3734960f
"mac80211: clean up ieee80211_hw_config errors"

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 7a7a6c1..7912eb1 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -396,8 +396,10 @@
 	 */
 	if (params->interval) {
 		sdata->local->hw.conf.beacon_int = params->interval;
-		ieee80211_hw_config(sdata->local,
-				    IEEE80211_CONF_CHANGE_BEACON_INTERVAL);
+		err = ieee80211_hw_config(sdata->local,
+					IEEE80211_CONF_CHANGE_BEACON_INTERVAL);
+		if (err < 0)
+			return err;
 		/*
 		 * We updated some parameter so if below bails out
 		 * it's not an error.