Input: max77650-onkey - add of_match table

We need the of_match table if we want to use the compatible string in
the pmic's child node and get the onkey driver loaded automatically.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>