dt-bindings: clock: Add RPMI clock service controller bindings

dt-bindings: clock: Add RPMI clock service controller bindings

Add device tree bindings for the RPMI clock service group based
controller for the supervisor software.

The RPMI clock service group is defined by the RISC-V platform
management interface (RPMI) specification.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Link: https://lore.kernel.org/r/20250818040920.272664-10-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>