ARM: ux500: move BU21013 touchpad GPIOs into top-level DTS

The BU21013 touchscreen GPIOs have been pretty confused, correct
them per board, and move the GPIO assignments up to the top
level DTS file so we can control it from there, and avoid defining
the GPIO assignments for non-ST UIB equipped boards.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>