s390: replace snprintf in show functions with sysfs_emit

s390: replace snprintf in show functions with sysfs_emit

show() must not use snprintf() when formatting the value to be
returned to user space.

Fix the coccicheck warnings:
WARNING: use scnprintf or sprintf.

Use sysfs_emit instead of scnprintf or sprintf makes more sense.

Signed-off-by: Qing Wang <wangqing@vivo.com>
Acked-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Acked-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/1634280655-4908-1-git-send-email-wangqing@vivo.com
[hca@linux.ibm.com: fix indentation]
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>