clk: rockchip: Restore the clock phase after the rate was changed

There are many factors affecting the clock phase, including clock
rate, temperature, logic voltage and silicon process, etc. But clock
rate is the most significant one here, and the driver should be aware
of the change of the clock rate. As mmc controller need a fixed phase
after tuning was completed, at least before explicitly doing re-tune,
so this patch try to restore the clock phase by monitoring the event
of rate change.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>