s390/cpum_sf: remove parameter in call to pr_err

The op argument is hardcoded in the parameter list of function pr_err.
Make the op code part of the text printed by pr_err.
No functional change.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>