ARM: dts: stm32: lxa-tac: add Linux Automation GmbH TAC

ARM: dts: stm32: lxa-tac: add Linux Automation GmbH TAC

The Linux Automation Test Automation Controller (LXA TAC)[1] is an embedded
software development tool built around the Octavo Systems OSD32MP15x SiP.

The device contains an eMMC for storage, a DSA-capable on board ethernet
switch with two external ports, dual CAN busses, a power switch to turn
a device under test on or off and some other I/O.

As of now there are two STM32MP157 based hardware generations (Gen 1 and
Gen 2) that have most of their hardware config in common.
In the future there will also be a STM32MP153 based hardware generation.

[1]: https://www.linux-automation.com/en/products/lxa-tac.html

Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>