dt-bindings: clock: rk3568: Add SCMI clock ids

dt-bindings: clock: rk3568: Add SCMI clock ids

The Trusted Firmware on RK3568 exposes 3 clocks via the SCMI clock
interface. Add descriptive IDs for them.

The clock ids are used in both the older vendor-binary TF-A, as well
as the recently merged upstream SCMI clock implementation.

Link: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/31265
Reviewed-by: Diederik de Haas <diederik@cknow-tech.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251103234926.416137-2-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>