gpsd: Disable systemd service only for HW21

gnss-mgr is only present on HW21 and therefor gpsd will not be started
on other HWs if the service is disabled.

Also the bitrate is configured by gnss-mgr so we must keep gpsd with
default bitrate detection mode.

recipes-connectivity/gpsd/gpsd_%.bbappend

@@ -31,8 +31,11 @@ do_install_append () {
 # place than expect.
 do_install_append() {
     install -p ${D}/usr/lib/gps/*.so ${D}/usr/lib/python2.7/site-packages/gps/
+}
+
+do_install_append_am335x_nmhw21() {
     sed -i "s/GPSD_OPTIONS=\"\(.*\)\"/GPSD_OPTIONS=\"\1 -s 115200\"/g" ${D}${sysconfdir}/default/gpsd.default
 }
 
 # Service is started by gnss-mgr
-SYSTEMD_AUTO_ENABLE="disable"
+SYSTEMD_AUTO_ENABLE_am335x-nmhw21 = "disable"