On behalf of : https://github.com/ikarostsin

Based on the implementation of RiscvFlushIcache::flush, the second parameter should be the end address rather than the size of the memory region.

```
void RiscvFlushIcache::flush(uintptr_t start, uintptr_t end) {
  long ret = sys_flush_icache(start, end, SYS_RISCV_FLUSH_ICACHE_ALL);
  guarantee_with_errno(ret == 0, "riscv_flush_icache failed");
```