riscv64/smp: Implement multi-processor support

* Working under qemu smp 1,2+
* Working on SiFive Unmatched
* x86_64 efi not broken by smp_boot_other_cpus change

Change-Id: I32ebc17913e46ed082be9ade8f56448bbf12f16e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4705
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

kernel/arch/debug: implement for riscv64

Change-Id: Iab5cc9ef4059f968bca03683592d1ec1818a26a2
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4053
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

kernel: Fill remaining riscv64 architecture headers