pinctrl: samsung: use __devinit section for init code

The samsung pinctrl driver has a probe function that is
__devinit and that calls a lot of other functions that are
marked __init, which kbuild complains about.

Marking everything __devinit means that the code does not
discarded when CONFIG_HOTPLUG is set, which is a little
more wasteful, but also more consistent

Without this patch, building exynos_defconfig results in:

WARNING: drivers/pinctrl/built-in.o(.devinit.text+0x124): Section mismatch in reference from the function samsung_pinctrl_probe() to the function .init.text:samsung_gpiolib_register()
The function __devinit samsung_pinctrl_probe() references
a function __init samsung_gpiolib_register().
If samsung_gpiolib_register is only used by samsung_pinctrl_probe then
annotate samsung_gpiolib_register with a matching annotation.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Abraham <thomas.abraham@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>