arm: apple: nvme: Add SART support and RTKit buffer management

The NVMe firmware in the macOS 13 beta blocks or crashes with u-boot's
current minimal RTKit implementation. It does not provide buffers for
the firmware's buffer requests. The ANS2 firmware included in macOS 11
and 12 tolerates this. The firmware included in the first macOS 13 beta
requires buffers for the crashlog and ioreport endpoints to function.

In the case of the NVMe the buffers are physical memory. Access to
physical memory is guarded by what Apple calls SART.
Import m1n1's SART driver (exclusively used for the NVMe controller).
Implement buffer management helpers for RTKit. These are generic since
other devices (none in u-boot so far) require different handling.

Signed-off-by: Janne Grunau <j@jannau.net>
Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Tested-by: Mark Kettenis <kettenis@openbsd.org>