udev: Rename all wlan interfaces wifiN and start scanning

This since the feature is called 'wifi' in Infix, this makes the naming
consistent over the system.

Also trigger start of a wpa_supplicant, for scanning in the background.
The scanning results is available operational.

board/common/rootfs/etc/udev/rules.d/70-rename-wifi.rules

@@ -0,0 +1 @@
+SUBSYSTEM=="net", ACTION=="add", TEST=="/sys/class/net/$name/wireless", NAME="wifi%n"

src/confd/bin/wifi-detected.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+if [ ! -e "/etc/wpa-supplicant-${INTERFACE}.conf" ]; then
+	cat <<EOF  > /etc/wpa-supplicant-${INTERFACE}.conf
+ctrl_interface=/run/wpa_supplicant
+update_config=0
+autoscan=periodic:10
+disable_scan_offload=1
+ap_scan=1
+# Empty network block to enable scanning without connecting
+bgscan="simple: 30:-45:300"
+
+EOF
+	cat <<EOF > /etc/finit.d/available/wpa-supplicant-${INTERFACE}.conf
+# Generated by Infix wifi interface detected
+service <!> name:wpa_supplicant :${INTERFACE} <> \
+	[2345] wpa_supplicant -s -i ${INTERFACE} -c /etc/wpa-supplicant-${INTERFACE}.conf \
+       -- WPA supplicant @${INTERFACE} (scanning only)
+
+EOF
+	initctl -bfqn enable wpa-supplicant-${INTERFACE}
+	initctl reload
+	TIMEOUT=300
+	status=$(wpa_cli -i ${INTERFACE} scan)
+	while [ "$status" != "OK" ]; do
+		status=$(wpa_cli -i ${INTERFACE} scan)
+		TIMEOUT=$((TIMEOUT-1))
+	        [ $TIMEOUT -eq 0 ] && logger -t wifi-detect "Failed to start scanning on $INTERFACE" && break
+		sleep 0.5
+	done
+fi