configs/imx8mn_bsh_smm_s2_pro_defconfig: new defconfig

BSH SMM S2 PRO (SystemMaster S2 Pro) Board is an add-on board which
provide input and output interfaces to a dedicated carrier board. It is
designed mainly to provide graphical/video and connectivity interfaces
to the appliance.

Board support package includes the following components:
- mainline Linux kernel 6.1.6
- mainline U-Boot 2022-07
- Default packages from buildroot

https://www.apertis.org/reference_hardware/imx8mn_bsh_smm_s2pro_setup/



Add Ariel D'Alessandro and Dario Binacchi as co-maintainer, we work
together on platform mainline

Build and tested using:
docker pull registry.gitlab.com/buildroot.org/buildroot/base:20220105.2314

Cc: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Heiko Thiery <heiko.thiery@gmail.com>
Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Tested-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>