systemd: Use overlay for specifying watchdog parameters

There's no reason to sed stuff. This way also makes it easier to support
running with empty /etc.

Change-Id: I16c0dba53682df574ee119951f47c7c6d4071d61
diff --git a/configs/czechlight_beaglebone_defconfig b/configs/czechlight_beaglebone_defconfig
index 7d7137f..97a7393 100644
--- a/configs/czechlight_beaglebone_defconfig
+++ b/configs/czechlight_beaglebone_defconfig
@@ -12,7 +12,7 @@
 BR2_TARGET_GENERIC_GETTY_PORT="ttyO0"
 # BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW is not set
 BR2_ROOTFS_OVERLAY="$(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/common/overlay/ $(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/beaglebone/overlay/"
-BR2_ROOTFS_POST_BUILD_SCRIPT="$(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/common/dhcp-network.sh $(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/common/systemd-watchdog.sh"
+BR2_ROOTFS_POST_BUILD_SCRIPT="$(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/common/dhcp-network.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="$(BR2_EXTERNAL_CZECHLIGHT_PATH)/board/czechlight/beaglebone/post-image.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y