ARM: nomadik: fix up SD/MMC DT settings

The DTSI file for the Nomadik does not properly specify how the
PL180 levelshifter is connected: the Nomadik actually needs all
the five st,sig-dir-* flags set to properly control all lines out.

Further this board supports full power cycling of the card, and
since this variant has no hardware clock gating, it needs a
ridiculously low frequency setting to keep up with the ever
overflowing FIFO.

The pin configuration set-up is a bit of a mystery, because of
course these pins are a mix of inputs and outputs. However the
reference implementation sets all pins to "output" with
unspecified initial value, so let's do that here as well.

Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>