dt-bindings: arm: ti: Add binding for Siemens IOT2050 SM variant

dt-bindings: arm: ti: Add binding for Siemens IOT2050 SM variant

This new variant is derived from the Advanced PG2 board, removing the
Arduino interface, and adding a new ASIC for communicating with the
PLC 1200 signal modules.

Signed-off-by: Su Bao Cheng <baocheng.su@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/595d8d79647a0f5e6e635a22ee0fee011f8a5c5e.1707463401.git.jan.kiszka@siemens.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>