ARM: SAMSUNG: local spi-core header in mach-s3c24xx

This patch moves spi-core header file into mach-s3c24xx.
Because it is not used for others except mach-s3c24xx.

Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>