dt-bindings: arm: rockchip: Add ArmSoM LM7 SoM

dt-bindings: arm: rockchip: Add ArmSoM LM7 SoM

LM7 is an System on Module made by ArmSoM based on Rockchip RK3588.
This SoM is used by W3 Board.

LM7 features:
- Rockchip RK3588
- LPDDR4x 4/8/16/32 GB
- eMMC 16/32/64/128 GB

Add devicetree binding for ArmSoM LM7 SoM.

Signed-off-by: Jianfeng Liu <liujianfeng1994@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240918165008.169917-2-liujianfeng1994@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>