clk: rmobile: Assure SD-IF clock are configured correctly

The SD driver calls clk_set_rate() before clk_enable(), yet clk_set_rate()
implementation in the clock driver does not set the SD-IF divider. Fix it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>