pinctrl: samsung: Include pinctrl-exynos driver data conditionally

Since pinctrl-samsung is a common part of the pin control support for
several Samsung SoCs, it can be compiled without Exynos support enabled.

This patch surrounds Exynos-specific driver data with ifdefs to include
them only when support for Exynos is enabled.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
[Fixed up EXYNOS4->EXYNOS]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>