The moxart defconfig wasn't even building a kernel for Moxart,
it was building a kernel for V4T on the nothing platform. Switch
to MULTI_V4 and keep the right drivers, update a few selections.
Now it (presumably) builds a minimalist Moxart kernel again.

Cc: Jonas Jensen <jonas.jensen@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>