Retry initial 20/40 MHz co-ex scan if the driver is busy

This makes the initial OBSS scans in AP mode before starting 40 MHz BSS
more robust. In addition, HT20 can be used as a backup option if none of
the scans succeed.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/ap/hostapd.h

@@ -363,6 +363,7 @@ struct hostapd_iface {
 #endif /* CONFIG_ACS */
 
 	void (*scan_cb)(struct hostapd_iface *iface);
+	int num_ht40_scan_tries;
 };
 
 /* hostapd.c */