mfd: janz-cmoio: 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 following coccicheck warning:
drivers/mfd/janz-cmodio.c:157: WARNING: use scnprintf or sprintf.

Use sysfs_emit instead of scnprintf or sprintf makes more sense.

Signed-off-by: Qing Wang <wangqing@vivo.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/1634280592-4722-1-git-send-email-wangqing@vivo.com