ACPI: button: fix some coding style issues

Fix some coding style issues reported by checkpatch.pl, including the
following types:

WARNING: Block comments use * on subsequent lines
WARNING: Block comments use a trailing */ on a separate line
ERROR: code indent should use tabs where possible

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>