s390: vmlogrdr: Use ARRAY_SIZE instead of reimplementing its function

Use the common code ARRAY_SIZE macro instead of a private implementation.
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/vmlogrdr.c

@@ -153,7 +153,7 @@ static struct vmlogrdr_priv_t sys_ser[] = {
 	}
 };
 
-#define MAXMINOR  (sizeof(sys_ser)/sizeof(struct vmlogrdr_priv_t))
+#define MAXMINOR  ARRAY_SIZE(sys_ser)
 
 static char FENCE[] = {"EOR"};
 static int vmlogrdr_major = 0;