cpumask: fix powernow-k8: partial revert of 2fdf66b4

Impact: fix powernow-k8 when acpi=off (or other error).

There was a spurious change introduced into powernow-k8 in this patch:
so that we try to "restore" the cpus_allowed we never saved.  We revert
that file.

See lkml "[PATCH] x86/powernow: fix cpus_allowed brokage when
acpi=off" from Yinghai for the bug report.

Cc: Mike Travis <travis@sgi.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>