William Johansson authored Apr 17, 2018 and Natanael Copa committed May 16, 2018

If Xen is present and Grub is used, like on UEFI systems, use multiboot2
to load Xen and the dom0 linux kernel.

Enable grub modules:
 * part_gpt: to read files from GPT partitions
 * multiboot2: to load multiboot2 kernels, like Xen
 * gzio: to load Xen which is gzip compressed