mfd/pinctrl: Delete platform data header

This deletes the special AB8500 GPIO platform data passing
header and merges the few remaining contents down into the
abx500 pinctrl driver which handles the abx500 GPIO device.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>