MIPS: mobileye: Add EyeQ6H device tree

EyeQ6H (or “High”) is an other SoC from Mobileye still based on the
MIPS I6500 architecture as the EyeQ5. The 2 clusters of this SoC
contains 4 cores which are capable of running 4 threads. Besides this,
it features multiple controllers such as the classic UART, high speed
I2C, SPI, as well as CAN-FD, PCIe Gen4, Octal/Quad SPI Flash
interface, Gigabit Ethernet, MIPI CSI-2, MIPI DSI, and eMMC 5.1. It
also includes a Hardware Security Module, Functional Safety Hardware,
and video encoders and more.

This commit provides the initial device tree files with support for
UART, GPIO and pinctrl, as well as fixed clocked.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>