spi: spi-s3c64xx: Drop unused enable_datapath() function argument

The spi pointer argument is not used now so remove it.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Andi Shyti <andi@etezian.org>
Signed-off-by: Mark Brown <broonie@kernel.org>