mmc: sdhci-s3c: Fix driver data for Exynos4 SoCs

Support for non-dt based initialization for Exynos SoCs has been removed,
so there is no need to keep driver IDs for this case. While touching this,
replace odd conditional code for instantiating driver data for Exynos4
SoCs with a simple reference and move that driver data under CONFIG_OF.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>