cpuidle: sysfs: Fix the overlap for showing available governors

When showing the available governors, it's "%s " in scnprintf(),
not "%s", so if the governor name has 15 characters, it will
overlap with the later one, fix it by adding one more for the
size.

While we are at it, fix the minor coding style issue and remove
the "/sizeof(char)" since sizeof(char) always equals 1.

Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>