spi: orion: Change spi-orion to use transfer_one() semantics for SPI transfers

This commit changes spi-orion to provide setup, set_cs, and transfer_one
functions instead of transfer_one_message. This allows chip select support
for both native and GPIO chip selects to be added.

Signed-off-by: Ken Wilson <ken.wilson@opengear.com>
Signed-off-by: Mark Brown <broonie@kernel.org>