arm: apple: Add initial Apple M2 Ultra support

Apple's M2 Ultra SoC are somewhat similar to the M1 Ultra but needs
a tweaked memory map as the M2 Pro/Max SoCs.  USB, NVMe, UART, WDT
and PCIe are working with the existing drivers.

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