s390/tape: remove unsupported PM functions

The power-management related functions are unused since
'commit 39421627 ("s390: remove broken hibernate / power
management support")'. Remove them from tape drivers.

Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>