mesh: Fix mesh interface removal fix

This wpa_drv_if_remove() call was previously modified to fix a different
issue, but that fix resulted in unconditional use of treed memory here
(wpa_supplicant_deinit_iface() frees wpa_s). Make a local copy of
wpa_s->parent to be able to use it after wpa_s is freed. The
mesh_if_created case has wpa_s->parent != wpa_s, so this should be
sufficient way of handling the wpa_drv_if_remove() call here.

Signed-off-by: Jouni Malinen <j@w1.fi>

wpa_supplicant/wpa_supplicant.c

@@ -5322,6 +5322,7 @@ int wpa_supplicant_remove_iface(struct wpa_global *global,
 #ifdef CONFIG_MESH
 	unsigned int mesh_if_created = wpa_s->mesh_if_created;
 	char *ifname = NULL;
+	struct wpa_supplicant *parent = wpa_s->parent;
 #endif /* CONFIG_MESH */
 
 	/* Remove interface from the global list of interfaces */
@@ -5357,7 +5358,7 @@ int wpa_supplicant_remove_iface(struct wpa_global *global,
 
 #ifdef CONFIG_MESH
 	if (mesh_if_created) {
-		wpa_drv_if_remove(wpa_s->parent, WPA_IF_MESH, ifname);
+		wpa_drv_if_remove(parent, WPA_IF_MESH, ifname);
 		os_free(ifname);
 	}
 #endif /* CONFIG_MESH */