CM-SOM-AM57X has two options of main storage devices - eMMC or NAND.
Add eMMC chip support (over MMC2 bus).
Signed-off-by: Dmitry Lifshitz <lifshitz@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Tony Lindgren <tony@atomide.com>