mac80211: Fix mesh-related build breakage...

net/mac80211/cfg.c: In function ‘sta_apply_parameters’:
net/mac80211/cfg.c:746: error: ‘struct sta_info’ has no member named ‘plink_state’
make[1]: *** [net/mac80211/cfg.o] Error 1
make: *** [net/mac80211/mac80211.ko] Error 2

Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index a2ff474..ed3400c 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -738,6 +738,7 @@
 						  &sta->sta.ht_cap);
 
 	if (ieee80211_vif_is_mesh(&sdata->vif)) {
+#ifdef CONFIG_MAC80211_MESH
 		if (sdata->u.mesh.security & IEEE80211_MESH_SEC_SECURED)
 			switch (params->plink_state) {
 			case PLINK_LISTEN:
@@ -758,6 +759,7 @@
 				mesh_plink_block(sta);
 				break;
 			}
+#endif
 	}
 }