Input: tc3589x-keypad - support probing from device tree

Implement device tree probing for the tc3589x keypad driver.
This is modeled on the STMPE keypad driver and tested on the
Ux500 TVK1281618 UIB.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>