PM: add kconfig option for deprecated .../power/state files

Add a new PM_SYSFS_DEPRECATED config option to control whether or
not the /sys/devices/.../power/state files are provided.  This will
make it easier to get rid of that mechanism when the time comes,
and to verify that userspace tools work right without it.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>