x86: Allow multiple values to be specified with "hpet="

This is particularly to be able to specify "hpet=force,verbose",
as "force" ought to be a primary candidate for also wanting to
use "verbose".

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/4F79D120020000780007C031@nat28.tlf.novell.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>