MMC_S3C isn't ready yet to be built with COMPILE_TEST, hence drop it.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200908140242.743234-1-ulf.hansson@linaro.orgReviewed-by: Krzysztof Kozlowski <krzk@kernel.org>