x86: add multiboot2 protocol support for relocatable images
Add multiboot2 protocol support for relocatable images. Only GRUB2 with
"multiboot2: Add support for relocatable images" patch understands
that feature. Older multiboot protocol (regardless of version)
compatible loaders ignore it and everything works as usual.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com> Acked-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Doug Goldstein <cardoe@cardoe.com>