mfd: Add support for COMe-cBL6 to Kontron PLD driver

This patch adds the DMI system ID of the Kontron COMe-cBL6 board to
the Kontron PLD driver. The list of supported products in the module
description is also updated.

Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
Acked-by: Christian Rauch <christian.rauch@kontron.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>