Similar as available for u-boot (ce2995e1dc) and syslinux (c5112c25e4), enable parsing and writing devicetree filename into grub.cfg. This is required by arm64-based devices running edk2 instead of u-boot as the main bootloader (e.g. 96boards HiKey and HiKey960). Signed-off-by: Ricardo Salveti <ricardo@foundries.io> Closes: #1790 Approved by: cgwalters