gpsdate: use systemd.bbclass

Also update SRCREV to one commit forward, which fixes installing the
service file when using systemctl enable (which OE uses).

recipes-extra/gpsdate/gpsdate_git.bb

@@ -12,13 +12,15 @@ PV = "0.2+git${SRCPV}"
 SRC_URI = "git://git.sysmocom.de/gpsdate.git;branch=master \
 	file://gpsdate.default \
 "
-SRCREV = "81690ca78e816f86e0da11bbe8cba725fa1a634d"
+SRCREV = "cd7b77ef311f317aac7a067308a94e46811a20f2"
 S = "${WORKDIR}/git"
 
 INITSCRIPT_NAME = "gpsdate"
 INITSCRIPT_PARAMS = "defaults 35"
 
-inherit update-rc.d
+inherit update-rc.d systemd
+
+SYSTEMD_SERVICE_${PN} = "${PN}.service"
 
 do_install() {
     install -d ${D}/${sbindir}
@@ -28,17 +30,12 @@ do_install() {
     install -m 0755 ${S}/gpsdate.init ${D}/${sysconfdir}/init.d/gpsdate
 
     install -d ${D}${systemd_system_unitdir}
-    install -d ${D}${systemd_system_unitdir}/multi-user.target.wants/
-
     install -m 0644 ${S}/gpsdate.service ${D}${systemd_system_unitdir}
-    ln -sf ../gpsdate.service ${D}${systemd_system_unitdir}/multi-user.target.wants/
 
     install -d ${D}/${sysconfdir}/default
     install -m 0644 ${WORKDIR}/gpsdate.default ${D}/${sysconfdir}/default/gpsdate
 }
 
-FILES_${PN} += "${systemd_unitdir}"
-
 PACKAGES =+ "gps-watchdog"
 
 FILES_gps-watchdog = "${sbindir}/gps-watchdog"