uboot-imx

mmc: s5p_sdhci: add the s5p_set_clock function

Add the s5p_set_clock function.
It's not good that "set_mmc_clk" is assigned directly.
In future, it should be changed to use the clock framework.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>