dt-bindings: clock: renesas,r9a09g056/57-cpg: Add XSPI core clock

dt-bindings: clock: renesas,r9a09g056/57-cpg: Add XSPI core clock

Add XSPI core clock definitions to the clock bindings for the Renesas
R9A09G056 and R9A09G057 SoCs. These clocks IDs are used to support XSPI
interface.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250627204237.214635-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>