mac80211: remove unimplemented mesh vendor sync

There's no vendor-specific mesh sync implemented
and there don't need to be dummy handlers that
only print messages, so remove that code. While
at it, also constify the mesh sync ops.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 02e4793..ebc1b5d 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -610,7 +610,7 @@
 		IEEE80211_MESH_SEC_SECURED = 0x2,
 	} security;
 	/* Extensible Synchronization Framework */
-	struct ieee80211_mesh_sync_ops *sync_ops;
+	const struct ieee80211_mesh_sync_ops *sync_ops;
 	s64 sync_offset_clockdrift_max;
 	spinlock_t sync_offset_lock;
 	bool adjusting_tbtt;