ARM: dts: k2g-evm: enable mmc/sd suppport

The K2G EVM from TI has an SD card slot as
well as onboard eMMC for data storage.

Enable support 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>