ARM: u300: Delete dummy SPI chip

It's been told to me a few times that this kernel module
should not exist, instead we should use the loopback test
from userspace if need be. If a kernel module is required
for testing SPI, it should be generic and put in
drivers/spi/*.

Delete this driver.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>