rockchip: add support for nanopc t6

rockchip: add support for nanopc t6

SoC: Rockchip RK3588
CPU: Quad-core ARM Cortex-A76(up to 2.4GHz) and quad-core Cortex-A55 CPU (up to 1.8GHz)
GPU: Mali-G610 MP4, compatible with OpenGLES 1.1, 2.0, and 3.2, OpenCL up to 2.2 and Vulkan1.2
VPU: 8K@60fps H.265 and VP9 decoder, 8K@30fps H.264 decoder, 4K@60fps AV1 decoder, 8K@30fps H.264 and H.265 encoder
NPU: 6TOPs, supports INT4/INT8/INT16/FP16
RAM: 64-bit 4GB/8GB/16GB LPDDR4X at 2133MHz
Flash: 32GB/64GB/256GB eMMC, at HS400 mode
microSD: support up to SDR104 mode
Ethernet: 2x PCIe 2.5G Ethernet

Signed-off-by: xiaobo tian <peterwillcn@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16158
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>