arm: dts: iot2050: Add support for M.2 variant

Add support for the M.2 board based on the iot2050 advanced board.
The board has two m.2 connectors, one is B-keyed, the other E-keyed.
The B-key slot can connect 5G/SSD devices, and E-key can be used for
WIFI/BT devices.

This variant is covered by PG2 firmware image.

Signed-off-by: chao zeng <chao.zeng@siemens.com>
[Jan: align DT to kernel, polish wording]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
diff --git a/configs/iot2050_pg2_defconfig b/configs/iot2050_pg2_defconfig
index d2bdeab..b206677 100644
--- a/configs/iot2050_pg2_defconfig
+++ b/configs/iot2050_pg2_defconfig
@@ -69,7 +69,7 @@
 # CONFIG_ISO_PARTITION is not set
 CONFIG_OF_CONTROL=y
 CONFIG_SPL_OF_CONTROL=y
-CONFIG_OF_LIST="k3-am6528-iot2050-basic-pg2 k3-am6548-iot2050-advanced-pg2"
+CONFIG_OF_LIST="k3-am6528-iot2050-basic-pg2 k3-am6548-iot2050-advanced-pg2 k3-am6548-iot2050-advanced-m2"
 CONFIG_SPL_MULTI_DTB_FIT=y
 CONFIG_SPL_OF_LIST="k3-am65-iot2050-spl"
 CONFIG_SPL_MULTI_DTB_FIT_NO_COMPRESSION=y