ARM: EXYNOS: Add spi clock support for EXYNOS5

Add support for clock instances for each spi controller.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Jaswinder Singh <jaswinder.singh@linaro.org>
[kgene.kim@samsung.com: changed the name of clk for consensus]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>