This adds support for the Linux Automation GmbH MC-1 board built around
the Octavo Systems OSD32MP157C-512M SiP.

The device tree is based on the one in linux-stm32/stm32-next, which
will probably be merged for Linux v5.8-rc1. Instead of waiting that
long, we import it here with some stuff removed/changed, so it's usable
for both barebox and Linux, without the prerequisite patches.

The non-barebox specific parts have been moved into separate DTSIs
(arch/arm/dts/stm32mp{157c-lxa-mc1,15xx-osd32}.dtsi), so both can be
dropped after the v5.8-rc1 sync with only include path change necessary
in arch/arm/dts/stm32mp157c-lxa-mc1.dts.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>