gpio: samsung: remove inclusion <mach/regs-clock.h>

The <mach/regs-clock.h> is not needed for gpio-samsung.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>