ARM: ux500: convert Snowball SPI pin reference

The SPI0 block is not at all connected to the AB8500 on the
Snowball: it is connected to the external header. These pins
on the header may also be used for GPIO, but let's assume
that SPI is a probable usecase on the Snowball and mux in the
SPI block and use these for SPI.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>