ARM: dts: keystone-k2g: add MMC0 and MMC1 nodes

Add device tree nodes for MMC0 and MMC1 pesent
on 66AK2G device.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
[nsekhar@ti.com: fix clock-names for mmc1 node]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>