efi_loader: create memory reservations in ACPI case

ACPI tables cannot convey memory reservations for ARM and RISC-V.
x86 uses the BIOS E820 table for this purpose. We cannot simply ignore the
device-tree when booting via ACPI. We have to assign EfiReservedMemory
according to the prior stage device-tree ($fdtaddr) or as fallback the
control device-tree ($fdtcontroladdr).

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>