arm: apple: Add initial Apple M2 support

Apple's M2 SoC very similar to the M1 and can use the same memory map.
The keyboard/trackpad on the MacBook Pro (13-inch, M2, 2022) uses
"dockchannel" as transport instead of SPI and needs a new driver.
USB, NVMe, uart, framebuffer and watchdog are working with the existing
drivers.

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