KVM: s390: selftests: Use TAP interface in the reset test

Let's standardize the s390x KVM selftest output to the TAP output
generated via the kselftests.h interface.

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20220531101554.36844-5-thuth@redhat.com


Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>