riscv: dts: allwinner: Add Dongshan Nezha STU devicetree

riscv: dts: allwinner: Add Dongshan Nezha STU devicetree

The 100ask Dongshan Nezha STU is a system-on-module that can be used
standalone or with a carrier board. The SoM provides gigabit Ethernet,
HDMI, a USB peripheral port, and WiFi/Bluetooth via an RTL8723DS chip.

The "DIY" carrier board exposes almost every pin from the D1 SoC to 0.1"
headers, but contains no digital circuitry, so it does not have its own
devicetree.

Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230126045738.47903-10-samuel@sholland.org
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>