board: iot2050: Support new IOT2050-SM variant

board: iot2050: Support new IOT2050-SM variant

Main differences between the new variant and Advanced PG2:

1. Arduino interface is removed. Instead, an new ASIC is added for
   communicating with PLC 1200 signal modules.
2. USB 3.0 type A connector is removed, only USB 2.0 type A connector is
   available.
3. DP interface is tailored down. Instead, to communicate with the
   PLC 1200 signal modules, a USB 3.0 type B connector is added but the
   signal is not USB.
4. DDR size is increased to 4 GB.
5. Two sensors are added, one tilt sensor and one light sensor.

Signed-off-by: Baocheng Su <[email protected]>
[Jan: rebased over OF_UPSTREAM]
Signed-off-by: Jan Kiszka <[email protected]>