s390: use scnprintf() in sys_##_prefix##_##_name##_show

snprintf() returns the number of bytes that would be written,
which may be greater than the the actual length to be written.

show() methods should return the number of bytes printed into the
buffer. This is the return value of scnprintf().

Link: https://lkml.kernel.org/r/20200509085608.41061-3-chenzhou10@huawei.comSigned-off-by: Chen Zhou <chenzhou10@huawei.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/kernel/ipl.c

@@ -181,7 +181,7 @@ static ssize_t sys_##_prefix##_##_name##_show(struct kobject *kobj,	\
 		struct kobj_attribute *attr,				\
 		char *page)						\
 {									\
-	return snprintf(page, PAGE_SIZE, _format, ##args);		\
+	return scnprintf(page, PAGE_SIZE, _format, ##args);		\
 }
 
 #define IPL_ATTR_CCW_STORE_FN(_prefix, _name, _ipl_blk)			\