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: 1ec2772e0c ("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>

arch/s390/kernel/diag.c

@@ -84,7 +84,7 @@ static int show_diag_stat(struct seq_file *m, void *v)
 
 static void *show_diag_stat_start(struct seq_file *m, loff_t *pos)
 {
-	return *pos <= nr_cpu_ids ? (void *)((unsigned long) *pos + 1) : NULL;
+	return *pos <= NR_DIAG_STAT ? (void *)((unsigned long) *pos + 1) : NULL;
 }
 
 static void *show_diag_stat_next(struct seq_file *m, void *v, loff_t *pos)