pwm: atmel-hlcdc: Fix module autoload for OF platform driver

This platform driver has a OF device ID table but the OF module alias
information is not created so module autoloading won't work.

This patch adds the missing MODULE_DEVICE_TABLE() for OF to export that
information so modules have the correct aliases built-in and autoloading
works correctly.

A longer explanation by Javier Canillas can be found here:
https://lkml.org/lkml/2015/7/30/519

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>