This patch fixes below build error when !CONFIG_OF_GPIO.

  CC      drivers/pinctrl/pinctrl-samsung.o
drivers/pinctrl/pinctrl-samsung.c: In function 'samsung_pinctrl_parse_dt_pins':
drivers/pinctrl/pinctrl-samsung.c:557:19: warning: unused variable 'prop' [-Wunused-variable]
drivers/pinctrl/pinctrl-samsung.c: In function 'samsung_gpiolib_register':
drivers/pinctrl/pinctrl-samsung.c:797:5: error: 'struct gpio_chip' has no member named 'of_node'
make[2]: *** [drivers/pinctrl/pinctrl-samsung.o] Error 1
make[1]: *** [drivers/pinctrl] Error 2
make: *** [drivers] Error 2

The samsung pinctrl driver supports only device tree enabled
platforms. Thus make PINCTRL_SAMSUNG depend on OF && GPIOLIB.

The reason to depend on GPIOLIB is CONFIG_OF_GPIO only available
when GPIOLIB is selected.

Since PINCTRL_EXYNOS4 select PINCTRL_SAMSUNG, thus also make
PINCTRL_EXYNOS4 depend on OF && GPIOLIB.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>