clk: mediatek: remove hdmitx_dig_cts from TOP clocks

The hdmitx_dig_cts clock signal is not a child of tvdpll_445p5m,
but is routed out of the HDMI PHY module.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>