spi: remove obsolete spi-s3c24xx-gpio driver

It was equivalent to spi-gpio, and there's no longer any in-tree users
of it, so get rid of it.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>