pinctrl: dt-bindings: samsung: add drive strength macros for Exynos5433

Commit 5db7e3bb ("pinctrl: dt-bindings: samsung: Add header with
values used for configuration") has added a header file for defining the
pinctrl values in order to avoid hardcoded settings in the Exynos
DTS related files.

Extend samsung.h to the Exynos5433 for drive strength values
which are strictly related to the particular SoC and may defer
from others.

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>