AP: Consider regulatory limitation when filling WMM element

In case the current channel has regulatory WMM limitations, take them
into account when filling the WMM element. Also check if the new WMM
element is different from the previous one and if so change the
parameter_set_count to imply stations to look into it.

Signed-off-by: Haim Dreyfuss <haim.dreyfuss@intel.com>

src/ap/hostapd.h

@@ -551,6 +551,9 @@ struct hostapd_iface {
 #ifdef CONFIG_AIRTIME_POLICY
 	unsigned int airtime_quantum;
 #endif /* CONFIG_AIRTIME_POLICY */
+
+	/* Previous WMM element information */
+	struct hostapd_wmm_ac_params prev_wmm[WMM_AC_NUM];
 };
 
 /* hostapd.c */