ARM: 5667/3: U300 SSP/SPI board setup and test

This adds a U300 board configuration for the PL022 SSP/SPI
PrimeCell driver recently merged to the 2.6.31-rc series.
Further it adds a dummy loopback SPI chip that can be used
for testing the SPI functionality on a running system using
the loopback mode of PL022.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>