mmc: host: tmio: disable clocks when unbinding

Create a helper function to disable clocks and use it in remove(), too.
Now, clk_summary in debugfs reports the clocks as disabled and
unprepared after unbinding.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>