spi: dt-bindings: at91: add microchip,lan9691-spi

Document Microchip LAN969x SPI compatible.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251229184004.571837-5-robert.marko@sartura.hr
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: robimarko

Documentation/devicetree/bindings/spi/atmel,at91rm9200-spi.yaml

@@ -19,6 +19,7 @@ properties:
       - const: atmel,at91rm9200-spi
       - items:
           - enum:
+              - microchip,lan9691-spi
               - microchip,sam9x60-spi
               - microchip,sam9x7-spi
               - microchip,sama7d65-spi