FT: Re-set PTK on reassociation

It turns out that this is needed for both FT-over-DS and FT-over-air
when using mac80211, so it looks easiest to just unconditionally
re-configure the keys after reassociation when FT is used.

src/ap/wpa_auth_i.h

@@ -116,7 +116,6 @@ struct wpa_state_machine {
 					   * Request */
 	u8 r0kh_id[FT_R0KH_ID_MAX_LEN]; /* R0KH-ID from FT Auth Request */
 	size_t r0kh_id_len;
-	int ft_over_ds;
 #endif /* CONFIG_IEEE80211R */
 };