MIPS: configs: ci20: Enable DMA and MMC support

Enable the SD/MMC support, along with DMA engine
support in the CI20 defconfig.

Acked-by: James Hogan <jhogan@kernel.org>
Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.co.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>