s390/diag: fix display of diagnose call statistics

Show the full diag statistic table and not just parts of it.

The issue surfaced in a KVM guest with a number of vcpus
defined smaller than NR_DIAG_STAT.

Fixes: 1ec2772e ("s390/diag: add a statistic for diagnose calls")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>