mmc: s3cmci: Drop redundant code in s3cmci_setup_data()

The in-parameter struct mmc_data *data is never NULL, because the caller
always provides a valid pointer. Hence drop the corresponding redundant
code.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200407143903.22477-1-ulf.hansson@linaro.org