fixup init.sh

Signed-off-by: Richard Weinberger <richard@nod.at>

init.sh

diff --git a/init.sh b/init.sh
index 4b39832..abf8761 100755
--- a/init.sh
+++ b/init.sh
@@ -17,7 +17,7 @@
 CMDLINE_SERIAL = "console=serial0,115200"
 RPI_EXTRA_CONFIG = "dtoverlay=disable-bt\n"
 WKS_FILE = "sdimage-its.wks"
-IMAGE_BOOT_FILES = "${BOOTFILES_DIR_NAME}/* \
-                 ${@make_dtb_boot_files(d)} \
-                 Image-initramfs-${MACHINE}.bin;kernel8.img"
+IMAGE_BOOT_FILES = "\${BOOTFILES_DIR_NAME}/* \
+                 \${@make_dtb_boot_files(d)} \
+                 Image-initramfs-\${MACHINE}.bin;kernel8.img"
 EOF