Input: tca8418 - fix loading this driver as a module from a device tree

Loading the tca8418 driver as a module on a device tree based system needs
a MODULE_ALIAS because the driver name does not match the automatic
name generation rules of a 'compatible' entry on i2c bus.

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>