use generic genimage buildroot script

board/funkey/post-build.sh

@@ -1,12 +1,4 @@
 #!/bin/sh
-BOARD_DIR="$( dirname "${0}" )"
-MKIMAGE="${HOST_DIR}/bin/mkimage"
-MKSWAP="${HOST_DIR}/sbin/mkswap"
-BOOT_CMD="${BOARD_DIR}/boot.cmd"
-BOOT_CMD_H="${BINARIES_DIR}/boot.scr"
-
-# U-Boot script
-"${MKIMAGE}" -C none -A arm -T script -d "${BOOT_CMD}" "${BOOT_CMD_H}"
 
 # Swap
 sed -i '/^\/swap/d' "${TARGET_DIR}/etc/fstab"