mac80211: fix processing HE capabilities (FS#3871)

Use the right argument to fix setting unsupported capabilities to 0

Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry-picked from commit 49ef4dbee5)

package/kernel/mac80211/files/lib/netifd/wireless/mac80211.sh

@@ -117,7 +117,7 @@ mac80211_add_he_capabilities() {
 		set -- $capab
 		[ "$(($4))" -gt 0 ] || continue
 		[ "$(((0x$2) & $3))" -gt 0 ] || {
-			eval "$4=0"
+			eval "$1=0"
 			continue
 		}
 		append base_cfg "$1=1" "$N"