[Feature] risc-v: 统一 PLIC 支持 | Unify the PLIC #9566
Description
Describe problem solved by the proposed feature
以下三个文件分别实现了 PLIC 驱动，可以统一到一个实现中。
- https://github.com/RT-Thread/rt-thread/blob/master/libcpu/risc-v/t-head/c906/plic.c
- https://github.com/RT-Thread/rt-thread/blob/master/libcpu/risc-v/t-head/c908/plic.c
- https://github.com/RT-Thread/rt-thread/blob/master/libcpu/risc-v/virt64/plic.c
Describe your preferred solution
No response
Describe possible alternatives
No response