gpio: samsung: Remove hardware.h inclusion

The contents of this header file are not referenced in the driver.
Remove its inclusion.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>