Add arch_ prefix to all atomic operations, and define ARCH_ATOMIC.
This enables KASAN instrumentation for all atomic operations on s390.

This is the s390 variant of commit 8bf705d1 ("locking/atomic/x86:
Switch atomic.h to use atomic-instrumented.h").
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>