gpio/samsung: Move SoC specific codes within macro

In drivers/gpio/gpio-samsung.c, there are certain structures
and functions which are not getting used if the particular
CPU is not selected. These code segments are moved under CPU
specific macros to remove compilation warnings.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>