risc-v: Allwinner D1 support

Add the Allwinnder D1 support provided by Rui-Xiang Guo and updated
but me.

https://mail-index.netbsd.org/port-riscv/2024/08/04/msg000127.html

Only driver listed as attaching in

https://github.com/picohive/netbsd-mangopi-mq-pro/blob/main/boot.log

have been added.

There is no need for the platform stuff as the board's u-boot is able
to load bootriscv64.efi and boot a generic kernel.

branches: 1.2.2;
risc-v: add a StarTech JH7100 SoC clock driver

The JH7100 is seen in the Beagle-V board.

RISC-V support that works on QEMU with a single hart.

Thanks for Simon Burge for plic(4).