clk: rockchip: Add CLK_SET_RATE_PARENT to aclk_cpu_pre

We'd like to be able to call clk_set_rate() on aclk_cpu (a gate) at
bootup.  In order for this to have any effect we need its parent
(aclk_cpu_pre) to percolate the rate change to _its_ parent
(aclk_cpu_src).  Add CLK_SET_RATE_PARENT to make this happen.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>