kobject: convert arm/mach-omap1/pm.c to kobj_attr interface

This makes the code a bit simpler and and gets us one step closer to
deleting the deprecated subsys_attr code.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Cliff Brake <cbrake@accelent.com>
Cc: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>