clk: rockchip: clk_rk3288: Implement "assign-clock-parent" and "assign-clock-rate"

clk: rockchip: clk_rk3288: Implement "assign-clock-parent" and "assign-clock-rate"

The RK3288 CRU-node assigns rates to a number of clocks that are not
implemented in the RK3288 clock-driver (but which have been
sufficiently initialised from rkclk_init()): for these clocks, we
implement the gmac clock set parent, but simply ignore the
others' set_rate() operation and return 0 to signal success.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>