Fix documentation and comment typo 'no_hz'

Change-Id: I37a670e1e9e9297b8eeb468088890bf174813818
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>