kernel/riscv: timer freq calculation, interrupt handling fixes

Change-Id: Ibe8b260a49c1b6e51df06f82b6c3a066c44accb1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6219
Reviewed-by: X512 <danger_mail@list.ru>
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

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/platform: implement for riscv64

Change-Id: Id1839ef39d927e6a2017c8b8ac3482d9eeb00fa1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4059
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

kernel/arch/timer: implement for riscv64

Change-Id: Ia854b0048a86b1427e975f482325ed4d4df1a12a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4061
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

riscv64: Fill in more bulk architecture items around libroot/kernel

Change-Id: Ia2a86d8814d06950ea2d2d19d966c642d26f81d6
Reviewed-on: https://review.haiku-os.org/c/1302
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>