ARM: davinci: da850: add OF_DEV_AUXDATA entry for mdio.

Add OF_DEV_AUXDATA for mdio driver in da850 board dt
file to use mdio clock.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>