loader/linux: Support passing RSDP address via boot params

loader/linux: Support passing RSDP address via boot params

Xen PVH guests will have the RSDP at an arbitrary address. Support that
by passing the RSDP address via the boot parameters to Linux.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Hans van Kranenburg <hans@knorrie.org>
Origin: upstream, https://git.savannah.gnu.org/cgit/grub.git/commit/?id=d170be42f12b0b2ab91d8d943d7b0bf563c906dd
Bug-Debian: https://bugs.debian.org/776450
Last-Update: 2019-01-07

Patch-Name: xen-pvh-rsdp-boot-params.patch

Gbp-Pq: Name xen-pvh-rsdp-boot-params.patch