ARM: S3C64XX: Tidy up common code in s3c64xx_spi_set_info()

The s3c64xx_spi_set_info() sets one of two platform data structures depending
on which controller is being specified. Change to taking a pointer to the
relevant platform data structure and then having one set of code to place
the data into the area being pointed to.

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