Copy sysmopcu.service to osmo-pcu

This way the name of systemd service file will match the name of the
binary similar to OsmoBTS. Add aliases so the user can use both old and
new names regardless of which file is installed. Once the corresponding
changes to OE recipes are applied old file can be removed.

Based on work by Pau Espin Pedrol <pespin@sysmocom.de>

Change-Id: I2ca6f6c486bd6fcf4d5b3d0a05d25dc04f020c26

contrib/osmo-pcu.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=sysmocom sysmoPCU
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/osmo-pcu -c /etc/osmocom/osmo-pcu.cfg
+Restart=always
+RestartSec=2
+RestartPreventExitStatus=1
+
+# The msg queues must be read fast enough
+CPUSchedulingPolicy=rr
+CPUSchedulingPriority=1
+
+[Install]
+WantedBy=multi-user.target
+Alias=sysmopcu.service

contrib/sysmopcu.service

@@ -14,3 +14,4 @@ CPUSchedulingPriority=1
 
 [Install]
 WantedBy=multi-user.target
+Alias=osmo-pcu.service