riscv: use atomic CSR bit set/clear operations, refactor

Fix race conditions that cause broken timer interrupts.

Change-Id: I78e13a18d394b1566977e894a1def16a66c9ca5f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5883
Reviewed-by: X512 <danger_mail@list.ru>
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

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/cpu: implement for riscv64

Change-Id: Ib4dd636f9ebb62931f77c809185ea810485d801e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4057
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

Fix definition of PAGESIZE and B_PAGE_SIZE

On sparc, the minimal page size we can use is 8K. Since B_PAGE_SIZE and
PAGESIZE defines were hardcoded to 4K, this resulted in a lot of
confusion in all code trying to manipulate pages.

- Remove cpu.h from headers/private/kernel/arch/*. It dates back from
NewOS and was not used anymore since our kernel uses B_PAGE_SIZE
(PAGE_SIZE was the only thing defined in this header).
- Add posix/arch/*/limits.h with the arch specific page size and include
it from the main limits.h.
- Adjust bios_ia32/debug.cpp which was the only place using the
PAGE_SIZE constant from the deleted headers.
- Change OS.h to define B_PAGE_SIZE to be the same as POSIX PAGESIZE.
- Define PAGESIZE in the build header if the host OS doesn't.

Change-Id: I8c3732cf952ea3c2f088aa16d216678fbf198b96
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3558
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

kernel/arch/riscv64: Correct some architecture headers

headers/riscv64: Implement basic arch headers

Change-Id: I6bfbacb61eae84ffebc30c2565683348d684d88f
Reviewed-on: https://review.haiku-os.org/c/1063
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>