PM: sleep: unmark 'state' functions as kernel-doc

Fix kernel-doc warnings in kernel/power/main.c by unmarking the
comment block as kernel-doc notation. This eliminates the following
kernel-doc warnings:

kernel/power/main.c:593: warning: expecting prototype for state(). Prototype was for state_show() instead
kernel/power/main.c:593: warning: Function parameter or member 'kobj' not described in 'state_show'
kernel/power/main.c:593: warning: Function parameter or member 'attr' not described in 'state_show'
kernel/power/main.c:593: warning: Function parameter or member 'buf' not described in 'state_show'

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