osmo-iuh: Add service file with startup fix

osmo-hnbgw sometimes starts too fast after msc/sgsn and then does not
reconnect. Fix this for now by sleeping before startup.
diff --git a/recipes-osmocom/osmo-iuh/osmo-iuh.inc b/recipes-osmocom/osmo-iuh/osmo-iuh.inc
index ca0c563..f1ce1ea 100644
--- a/recipes-osmocom/osmo-iuh/osmo-iuh.inc
+++ b/recipes-osmocom/osmo-iuh/osmo-iuh.inc
@@ -4,7 +4,8 @@
 LICENSE = "AGPLv3+"
 LIC_FILES_CHKSUM = "file://COPYING;md5=73f1eb20517c55bf9493b7dd6e480788"
 
-SRC_URI = "file://osmo-hnbgw.init"
+SRC_URI = "file://osmo-hnbgw.init \
+	   file://osmo-hnbgw.service"
 
 INC_PR = "r1.${META_TELEPHONY_OSMO_INC}"
 
@@ -32,6 +33,8 @@
 		install -m 0644 ${S}/contrib/systemd/$i ${D}${systemd_unitdir}/system/
 	done
 
+	install -m 0644 ${WORKDIR}/osmo-hnbgw.service ${D}${systemd_unitdir}/system/
+
 	install -d ${D}/var/lib/osmocom
 }