Add support for NanoPi R76S

[SuperKali]

This PR adds initial device tree support for the FriendlyELEC NanoPi R76S, based on the Rockchip RK3576 SoC.
It enables board bring-up and basic functionality.

Hardware Highlights

• SoC: RK3576 (4× Cortex-A72 + 4× Cortex-A53)
• GPU: Mali-G52 MC3 (OpenGL ES 3.2, Vulkan 1.2, OpenCL 2.0)
• NPU: 6 TOPS INT8
• RAM: 2GB / 4GB LPDDR4X / 16GB LPDDR5
• Storage: 32GB eMMC, microSD (UHS-I)
• Networking: Dual 2.5GbE, optional M.2 SDIO Wi-Fi
• USB: 1 × USB 3.2 Gen1 Type-A
• HDMI: 1.4/2.0, up to 4K@60Hz, 10-bit Deep Color
• Debug: UART 3.3V, 1.5 Mbps
• GPIO / Buttons: LEDs, User button, Power button, RTC battery connector
• Power: USB-C 5V

✅ Tested

• Boot and basic board bring-up
• UART console working
• eMMC detected and bootable
• microSD detected
• Dual 2.5GbE interfaces functional
• USB 3.2 port operational
• HDMI output working (framebuffer)
• Power and user buttons working
• Wi-Fi via M.2 SDIO module