arm64: dts: ti: Add support for Siemens IOT2050 boards

Add support for two Siemens SIMATIC IOT2050 variants, Basic and
Advanced. They are based on the TI AM6528 GP and AM6548 SOCs HS, thus
differ in their number of cores and availability of security features.
Furthermore the Advanced version comes with more RAM, an eMMC and a few
internal differences.

Based on original version by Le Jin.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://new.siemens.com/global/en/products/automation/pc-based/iot-gateways/simatic-iot2050.html
Link: https://github.com/siemens/meta-iot2050
Link: https://lore.kernel.org/r/4fb05969102d14d230e03ca4312ef9706efa61e6.1615473223.git.jan.kiszka@siemens.com