mfd: mt6397: Add platform device ID table

The platform bus_type .match callback attempts to match the platform device
name with an entry on the .id_table if provided and fallbacks to match with
the driver's name if a table is not provided.

Using a platform device ID to match is more explicit, allows the driver to
support more than one device and also the MODULE_DEVICE_TABLE macro can be
used to export the module aliases information instead of the MODULE_ALIAS.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>