meta-lxatac-bsp: rauc: add placeholder for polling section to system.conf

The polling information (interval, URL, auto-install behaviour, etc.)
is only known to the tacd. To pass them to RAUC the tacd will read the
config in `/usr/lib/rauc/system.conf` replace the placeholder added
in this commit with a proper polling secion and place the result
in `/run/rauc/system.conf`. After a deamon restart RAUC can handle
update polling and installation on its own.

Signed-off-by: Leonard Göhrs <[email protected]>

Author: hnez

meta-lxatac-bsp/recipes-core/rauc/files/lxatac/system.conf

@@ -1,3 +1,10 @@
+# WARNING: this file is read by the tacd and used as a template to generate a
+# version with additional update polling configuration.
+# The original file is placed in `/usr/lib/rauc/system.conf`, while the runtime
+# version is placed in `/run/rauc/system.conf`.
+# The latter may not exist if polling is not enabled and thus no special
+# runtime config is required.
+
 [system]
 compatible=Linux Automation GmbH - LXA TAC
 bootloader=barebox
@@ -13,6 +20,8 @@ system-info=/usr/lib/rauc/system-info-handler.sh
 [streaming]
 send-headers=boot-id;system-version;serial;transaction-id;uptime
 
+# <tacd-poll-section>
+
 [slot.rootfs.0]
 device=/dev/disk/by-partuuid/e82e6873-62cc-46fb-90f0-3e936743fa62
 type=ext4