arm: dts: apple: Add u-boot,dm-pre-reloc properties

These are necessary to make sure the power domains needed for the
serial console are availble in the pre-relocation phase.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>