input: serio: remove bus usage of dev_attrs

The dev_attrs field of struct bus_type is going away soon, so move the
remaining sysfs files that are being described with this field to use
dev_groups instead.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: <linux-input@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>