ARM: mvebu: Enable nfsroot in the defconfig

NFSroot is very frequently used by developers to boot, so let's make
our lives simpler and enable it by default.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Link: https://lkml.kernel.org/r/1396539014-8673-1-git-send-email-ezequiel.garcia@free-electrons.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>