pinctrl: add samsung pinctrl and gpiolib driver

Add a new device tree enabled pinctrl and gpiolib driver for Samsung
SoC's. This driver provides a common and extensible framework for all
Samsung SoC's to interface with the pinctrl and gpiolib subsystems. This
driver supports only device tree based instantiation and hence can be
used only on those Samsung platforms that have device tree enabled.

This driver is split into two parts: the pinctrl interface and the gpiolib
interface. The pinctrl interface registers pinctrl devices with the pinctrl
subsystem and gpiolib interface registers gpio chips with the gpiolib
subsystem. The information about the pins, pin groups, pin functions and
gpio chips, which are SoC specific, are parsed from device tree node.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>