ACPI: replace snprintf() in "show" functions with sysfs_emit()

coccicheck complains about the use of snprintf() in sysfs "show"
functions:

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

so use sysfs_emit() instead of it where applicable.

Signed-off-by: Qing Wang <wangqing@vivo.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>