intel-idle: convert to x86_cpu_id auto probing

With this it should be automatically loaded on suitable systems by
udev.

The old switch () is replaced with a table based approach, this
also cleans up the code.

Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>