automated: linux: factory-reset: fix device registration

Enable proper auto-registration with tag. Note: this patch requires
support in the lmp-device-auto-register script. Example support is
presented in this pull request:
foundriesio/meta-lmp#1227

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@foundries.io>

automated/linux/factory-reset/prepare-reset.sh

@@ -50,7 +50,7 @@ chmod 755 /var/sota/aklite-callback.sh
 mkdir -p /etc/sota/conf.d
 cp z-99-aklite-callback.toml /etc/sota/conf.d/
 if [ -n "${LABEL}" ]; then
-    echo "tags = \"${LABEL}\"" >> /etc/sota/conf.d/z-99-aklite-callback.toml
+    echo "${LABEL}" >> /etc/sota/tag
 fi
 # create signal files
 touch /var/sota/ota.signal