mach-s3c2410: remove unused spi-gpio.h file

Not used anymore as the spi_s3c24xx_gpio driver is gone (replaced by
the generic spi-gpio).

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>