mmc: sunxi: Disable sample clks on remove

When support for the sample clks was added calls to prepare_enable
were added to the probe path, but matching calls to disable_unprepare
were forgotten in the remove path, this fixes this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>