verdin-imx8mm/verdin-imx8mp: move imx verdins to OF_UPSTREAM

Move verdin-imx8mm and verdin-imx8mp to OF_UPSTREAM:
- handle the fact that dtbs now have a 'freescale/' prefix
- imply OF_UPSTREAM
- remove redundant files from arch/arm/dts leaving only the
  *-u-boot.dtsi files
- update MAINTAINERS files

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
14 files changed