wifi: mac80211: reject per-band vendor elements with MLO

The MLME code doesn't currently handle adding vendor elements
correctly with multi-link due to element inheritance. Simply
prevent that for now completely, if someone needs it we can
fix this later.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250101070249.bb82d3aaf6ef.Ib30573d0666430a3d7a905e513dfc661edf0bf65@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -1310,6 +1310,11 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 			    sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40 &&
 			    !(iftd->he_cap.he_cap_elem.phy_cap_info[0] & he_40_mhz_cap))
 				return -EINVAL;
+
+			/* no support for per-band vendor elems with MLO */
+			if (WARN_ON(iftd->vendor_elems.len &&
+				    hw->wiphy->flags & WIPHY_FLAG_SUPPORTS_MLO))
+				return -EINVAL;
 		}
 
 		/* HT, VHT, HE require QoS, thus >= 4 queues */