ARM: ux500: move SPI pin config to device tree

This moves the SPI pin control table out of the board file
and into the device tree. Move the specific setting for
SSP0 on the HREFprev60 into the prev60-specific DTS file.
The SPI2 configuration is not really connected to any device,
as it will conflict with GPIO218 which is used on all HREFs.

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