efi_loader: carving out memory reservations

The "Devicetree Specification 0.2" does not prescribe that memory
reservations must be EFI page aligned. So let's not make such an
assumption in our code.

Do not carve out the pages for the device tree. This memory area is
already marked as EFI_RUNTIME_SERVICES_DATA.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>