mmc: dw_mmc: Add dependency on DMA

The dw_mmc drivers rely on the DMA API, so update the Kconfig entry
to depend on HAS_DMA.  Since the drivers should build on any platform
with DMA, allow the driver to compile tested on non-ARC/ARM platforms.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>