libata: add CONFIG_PM to libata core layer
Conditionalize all PM related stuff in libata core layer using
CONFIG_PM.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
authored by Tejun Heo and committed by Jeff Garzik 6ffa01d8 438ac6d5