pinctrl: generic: add input schmitt disable parameter

In Marvell PXA/MMP silicons, input schmitt disable value is 0x40, not 0.
So append new config parameter -- input schmitt disable.

Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>