From: Rusty Russell <rusty@rustcorp.com.au>

Anton: breaks PPC64, as it needs cpu_possible_mask, but fix is already
in Ameslab tree.

The for_each_cpu() and for_each_online_cpu() iterators take a mask, and
noone uses them that way (except for arch/i386/mach-voyager, which uses
for_each_cpu(cpu_online_mask).  Make them more usable iterators, by
dropping the "mask" arg.

This requires that archs provide a cpu_possible_mask: most do, but PPC64
doesn't, so it is broken by this patch.  The other archs use a #define to
define it in asm/smp.h.

Most places doing loops over cpus testing for cpu_online() should use
for_each_cpu: it is synonymous at the moment, but with the CPU hotplug
patch the difference becomes important.

Followup patches will convert users.