mac80211: Fix compilation error when mesh is disabled

Wrap mesh sections inside CONFIG_MAC80211_MESH to fix compilation
problems reported by Stephen Rothwell, Larry Finger and Bruno Randolf.
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/main.c

@@ -245,10 +245,12 @@ void ieee80211_bss_info_change_notify(struct ieee80211_sub_if_data *sdata,
 				sdata->vif.bss_conf.enable_beacon =
 					!!sdata->u.ibss.presp;
 				break;
+#ifdef CONFIG_MAC80211_MESH
 			case NL80211_IFTYPE_MESH_POINT:
 				sdata->vif.bss_conf.enable_beacon =
 					!!sdata->u.mesh.mesh_id_len;
 				break;
+#endif
 			default:
 				/* not reached */
 				WARN_ON(1);