arm: dts: am33xx: Sync dts with Linux 4.20.0

arm: dts: am33xx: Sync dts with Linux 4.20.0

This patch synchronizes the am33xx SoC specific files with those from
Linux 4.20.0. Hence all board maintainers of am33xx based boards are
on the cc list.
The main purpose of this patch is to prevent further diverging of the
dts files from U-Boot and those from Linux. It aims to set the stage
for the synchronization of board specific dts files. Example: I'm the
maintainer of the PDU001 board: once this patch is applied successfully
I will make changes to the board specific dts file in Linux only and
then post a patch with a copy of this exact dts file to U-Boot. This
will make U-Boot and Linux remain in sync.
The stumbling block of https://patchwork.ozlabs.org/patch/943627 was
removed by the patch https://patchwork.ozlabs.org/patch/962428 from
Lokesh Vutla (many thanks!). This omap-serial driver allows using the
Linux am33xx.dtsi file in U-Boot.
Other changes to dts and dtsi files made by this patch are mainly to
prevent _new_ warnings during the build process. Especially the warning
at pinmux@800 stating 'unnecessary #address-cells/#size-cells without
"ranges" or child "reg"' was not removed. This warning is a good example
showing the benefit of the synchronization: if it needs to be fixed it
will be fixed in Linux and ported back to U-Boot.
Buildman reports all 46 am33xx SoC based boards to build fine, with
warnings of course. Nevertheless this patch should be tested thoroughly
on as many boards as possible to prevent any collateral damage.

Signed-off-by: Felix Brack <fb@ltec.ch>
Reviewed-by: Tom Rini <trini@konsulko.com>