clk: rockchip: Allow the RK3288 SPDIF clocks to change their parent

The clock branches leading to sclk_spdif and sclk_spdif_8ch on RK3288
SoCs only feed those clocks, allow those clocks to change their parents
all the way up the hierarchy.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>