ARM: dts: K2G: Add support for MMC controller

K2G SoC from TI has two MMC/SD controllers.
Add device tree data for these.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>