dt-bindings: rtc: at91rm9200: add sam9x7 compatible

Add compatible for SAM9X7 RTC.
Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230728102710.266457-1-varshini.rajendran@microchip.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

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

@@ -14,13 +14,17 @@ maintainers:
 
 properties:
   compatible:
-    enum:
-      - atmel,at91rm9200-rtc
-      - atmel,at91sam9x5-rtc
-      - atmel,sama5d4-rtc
-      - atmel,sama5d2-rtc
-      - microchip,sam9x60-rtc
-      - microchip,sama7g5-rtc
+    oneOf:
+      - enum:
+          - atmel,at91rm9200-rtc
+          - atmel,at91sam9x5-rtc
+          - atmel,sama5d4-rtc
+          - atmel,sama5d2-rtc
+          - microchip,sam9x60-rtc
+          - microchip,sama7g5-rtc
+      - items:
+          - const: microchip,sam9x7-rtc
+          - const: microchip,sam9x60-rtc
 
   reg:
     maxItems: 1