ARM: DTS: da850: Enable DMA use for MMC0

Add the needed bindings for MMC0 in order to be able to utilize the DMA
instead of PIO mode.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Sushaanth Srirangapathi <sushaanth.s@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>