Partially revert "mtd: nand: pxa3xx: Introduce 'marvell,armada370-nand' compatible string"

This partially reverts c0f3b864

.

The "armada370-nand" compatible support is not complete, and it was mistake
to add it. Revert it and postpone the support until the infrastructure is
in place.

Cc: <stable@vger.kernel.org> # 3.12
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>