s390x: remove double compat statement

s390x: remove double compat statement

We chain our compat handler via the CCW_COMPAT macros and via the
class_init function. (e.g. ccw_machine_2_7_class_options calls
ccw_machine_2_8_class_options). As all class_init functions in that
chain call SET_MACHINE_COMPAT for their compat settings, and
SET_MACHINE_COMPAT will append there is no need to do that again.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>