ARM: Kirkwood: fix unused mvsdio gpio pins

mvsdio_platform_data allows to pass card detect and write protect gpio
numbers to the driver. Some kirkwood boards don't use both pins as they
are not connected, and don't set the corresponding value in platform_data.

This will leave the unset values in platform_data initialized as 0, which
is in fact a valid gpio pin. mvsdio will grab that pin and configure it as
gpio, which in turn breaks nand controller as mpp0 also carries nand_io2.

This patch fixes the above by initializing unused gpio functions in the
platform_data with an invalid (-1) value.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Reported-by: Soeren Moch <smoch@web.de>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>