s390/cio: remove pm support from ccw bus driver

As part of removing broken pm-support from s390 arch, remove
the pm callbacks from ccw-bus driver.The power-management functions
are unused since the 'commit 39421627

 ("s390: remove broken
hibernate / power management support")'.

Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>