acpi throttling: Use this_cpu_has and simplify code current cpu

With the this_cpu_xx we no longer need to pass an acpi
structure to the msr management code. Simplifies code and improves
performance.

NOTE: This code is x86 specific (see #ifdef CONFIG_X86) but not under
      arch/x86.

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>