mmc: mmci: Drop unnecessary clear of variant->qcom_dml flag

There's no point clearing the variant flag in case the qcom variant fails
to setup DMA. This is because if mmci_dma_setup() fails, then the use_dma
flag remains set to false, which leads to mmci using PIO mode and not DMA.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>