Documentation: power: fix pm_qos_interface.rst format warning

Fix Sphinx warnings by indenting the bullet list (and making it
unnumbered).

Documentation/power/pm_qos_interface.rst:12: WARNING: Unexpected indentation.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>