dt-bindings: clock: cirrus,cs2000-cp: Document CS2500

dt-bindings: clock: cirrus,cs2000-cp: Document CS2500

Document backward compatibility support for the CS2500 chip, which is a
drop-in replacement for the CS2000 chip.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260504144534.43745-4-marek.vasut+renesas@mailbox.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>