power: domain: apple: Add reset support

The power management controller found on Apple SoCs als provides
a way to reset all devices within a power domain. This is needed
to cleanly shutdown the NVMe controller before we hand over
control to the OS.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested on: Macbook Air M1
Tested-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>