mmc: sh_mmcif: separate sh_mmcif_clk_update() into setup and prepare
Current sh_mmcif_clk_update() is called from probe() and set_ios(),
but, the purpose of later one is just clk_prepare_enable().
No need to setup mmc->f_max/f_min in many times.
This patch separe sh_mmcif_clk_update() into clk_prepare_enable()
and mmc->f_max/f_min setup.