dt-bindings: gpio: fsl,qoriq-gpio: Add missing mpc8xxx compatibles

The fsl,mpc8349-gpio, fsl,mpc8572-gpio, and fsl,mpc8610-gpio compatibles
are already documented in fsl,qoriq-gpio.yaml. Add the additional
compatibles that use fsl,mpc8349-gpio as a fallback. With that,
the 8xxx_gpio.txt binding document is redundant and can be removed.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/20250714202941.3013390-1-robh@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: robherring

Documentation/devicetree/bindings/gpio/8xxx_gpio.txt

@@ -29,6 +29,13 @@ properties:
               - fsl,ls1088a-gpio
               - fsl,ls2080a-gpio
           - const: fsl,qoriq-gpio
+      - items:
+          - enum:
+              - fsl,mpc8308-gpio
+              - fsl,mpc8377-gpio
+              - fsl,mpc8378-gpio
+              - fsl,mpc8379-gpio
+          - const: fsl,mpc8349-gpio
 
   reg:
     maxItems: 1