spi: spi_s3c24xx must initialize bus_num

Pass the bus number we expect the S3C24XX SPI driver to attach to via the
platform data.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>