s390/zfcp: remove pm support from zfcp driver

As part of removing the power management support from
s390 arch, remove PM callbacks from the scsi/zfcp driver.

Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>