mmc: dw_mmc-rockchip: dt-binding: Add tuning related things

Add ciu_drive, ciu_sample clocks and default-sample-phase. This will later
be used by tuning code.

We do not touch ciu_drive (and by extension define default-drive-phase).
Drive phase is mostly used to define minimum hold times, while one could
write some code to determine what phase meets the minimum hold time
(ex 10 degrees) this will not work with the current clock phase framework
(which floors angles, so we'll get 0 deg, and there's no way to know what
resolution the floors happen at). We assume that the default drive angles
set by the hardware are good enough.

Signed-off-by: Alexandru M Stan <amstan@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>