Revert "mmc: dw_mmc: rockchip: select proper card clock"

The origin patch get rockchip dwmmc by name 'ciu', which lead
to the SPL not able to remove 'clock-names' node in dts.
I'm not saying this is not correct, but I would prefer to handle
this in dts or clock driver to save memory for SPL.
For example the rk3288 SPL size has out of memory if not enable
BACK_TO_BROM option, there are many other SoCs has less internal
memory than rk3288.

This reverts commit 480a9b83.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>