modem_gps.sh: Add a script to use the WWAN modem GPS

By moving the AUX BM818 antenna connector to the unmarked center position
the modem can get a GPS signal. This NOT the GNSS controlled by HKS but is
part of the WWAN modem so is bound to the modem firmware and the WWAN HKS.
Signed-off-by: Angus Ainslie <angus@akkea.ca>

usr/bin/modem_gps.sh

+#!/bin/bash
+# gpsd doesn't wnat to share with ModemManger so give it a fifo instead
+# To get this to work you need to modify /etc/default/gpsd to
+# monitor "/tmp/gps". You also need to move the AUX BM818 antenna connection
+# to the center unmarked position.
+
+DEVICE="/dev/ttyUSB1"
+FIFO="/tmp/gps"
+
+rm ${FIFO}
+mkfifo ${FIFO}
+
+printf "AT+GPSSTART\r\n" > ${DEVICE}
+cat ${DEVICE} > ${FIFO} &
+systemctl restart gpsd
+#echo "AT+GPSSTOP" > ${DEVICE}