ARM: S5P[v210|c100|64x0]: Fix build error

gpio-samsung.h header file introduced by commit 93177be0910c
("ARM: S3C[24|64]xx: move includes back under <mach/> scope")
is required only by S3C[24|64]xx machines. Include them conditionally
to avoid the following build errors for other machine configurations.
drivers/gpio/gpio-samsung.c:35:31: fatal error: mach/gpio-samsung.h: No such file or directory
arch/arm/plat-samsung/pm-gpio.c:22:31: fatal error: mach/gpio-samsung.h: No such file or directory

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>