arm: exynos: clock: Remove exynos4x12_set_mmc_clk function

arm: exynos: clock: Remove exynos4x12_set_mmc_clk function

exynos4x12_set_mmc_clk function have been removed.
Because, exynos4x12_clock and exynos4_clock return same div_fsys* value.

Signed-off-by: Beomho Seo <beomho.seo@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Tested-by: Piotr Wilczek <p.wilczek@samsung.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Piotr Wilczek <p.wilczek@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>