PM: Add and use pr_fmt()

Prefix all printk/pr_<level> messages with "PM: " to make the
logging a bit more consistent.

Miscellanea:

 o Convert a few printks to pr_<level>
 o Whitespace to align to open parentheses
 o Remove embedded "PM: " from pr_debugs as pr_fmt adds it

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>