efi_loader: put device tree into EfiACPIReclaimMemory

According to the UEFI spec ACPI tables should be placed in
EfiACPIReclaimMemory. Let's do the same with the device tree.

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Grant Likely <grant.likely@arm.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>