This stops the driver from trying to probe the ATA slave
interface. The vendor code enables the slave interface
but the driver in the vendor tree does not make use of
it.

Setting it to muxmode 0 disables the slave interface:
the hardware only has the master interface connected
to the one harddrive slot anyways.

Without this change booting takes excessive time, so it
is very annoying to end users.

Fixes: dd5c0561 ("ARM: dts: Add basic devicetree for D-Link DNS-313")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>