ARM: S3C64XX: SPI: Define SPI controller devices

Platform devices for SPI Controller of S3C64XX are defined and exported for
machines to include. Also, controller setup helper functions are defined for
machine code to set runtime configuration of the controller and the bus.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>