pinctrl: Adds slew-rate, input-enable/disable

This commit adds slew-rate and input-enable/disable support for pinconf
-generic.

Signed-off-by: Sherman Yin <syin@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --cc Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
Simple merge

diff --cc drivers/pinctrl/pinconf-generic.c
Simple merge

diff --cc include/linux/pinctrl/pinconf-generic.h
Simple merge