ARM: board: cm-fx6: fix mmc for old revisions of utilite

ARM: board: cm-fx6: fix mmc for old revisions of utilite

Old revisions of Utilite (based on cm-fx6) do not have a dedicated
card detect pin. But the card is removable by the user and card
detection can be realized with polling (e.g. supported by Linux).

Add the broken-cd property to the mmc device tree instead of the
non-removable property to make card detection possible if polling
is supported.

Signed-off-by: Christopher Spinrath <christopher.spinrath@rwth-aachen.de>
Acked-by: Nikita Kiryanov <nikita@compulab.co.il>