GPIO: gpio-twl6040: Remove support for legacy (pdata) mode

TWL6040 is used only with OMAP4/5 SoCs and they can only boot in in DT mode.
The support for pdata/legacy boot can be removed.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>