arm: mx6: cm-fx6: modify device tree for old revisions of utilite

arm: mx6: cm-fx6: modify device tree for old revisions of utilite

Old revisions of Utilite (a miniature PC based on cm-fx6) do not have
a card detect for mmc, and thus the kernel needs to be told that
there's a persistent storage on usdhc3 to force it to probe the mmc
card.

Check the baseboard revision and modify the device tree accordingly
if needed.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>