clk: rockchip: implement linked gate clock support

clk: rockchip: implement linked gate clock support

Recent Rockchip SoCs have a new hardware block called Native Interface
Unit (NIU), which gates clocks to devices behind them. These clock
gates will only have a running output clock when all of the following
conditions are met:

1. the parent clock is enabled
2. the enable bit is set correctly
3. the linked clock is enabled

To handle them this code registers them as a normal gate type clock,
which takes care of condition 1 + 2. The linked clock is handled by
using runtime PM clocks. Handling it via runtime PM requires setting
up a struct device for each of these clocks with a driver attached
to use the correct runtime PM operations. Thus the complete handling
of these clocks has been moved into its own driver.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20241211165957.94922-5-sebastian.reichel@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>