dt-bindings: gpio-mmio: Correct opencores GPIO

In commit f48b5e8bc2 ("dt-bindings: gpio-mmio: Add compatible string
for opencores,gpio") we marked opencores,gpio to be allowed with
brcm,bcm6345-gpio. This was wrong, opencores,gpio is not compatible with
brcm,bcm6345-gpio. It has a different register map and is 8-bit vs
Broadcom which is 32-bit. Change opencores,gpio to be a separate
compatible string for MMIO GPIO.

Also, as this change rewrote the entire enum, I took this opportunity to
alphabetically sort the list.

Fixes: f48b5e8bc2 ("dt-bindings: gpio-mmio: Add compatible string for opencores,gpio")
Signed-off-by: Stafford Horne <shorne@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260115151014.3956805-2-shorne@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Documentation/devicetree/bindings/gpio/gpio-mmio.yaml

@@ -18,16 +18,12 @@ description:
 
 properties:
   compatible:
-    oneOf:
-      - enum:
-          - brcm,bcm6345-gpio
-          - ni,169445-nand-gpio
-          - wd,mbl-gpio # Western Digital MyBook Live memory-mapped GPIO controller
-          - intel,ixp4xx-expansion-bus-mmio-gpio
-      - items:
-          - enum:
-              - opencores,gpio
-          - const: brcm,bcm6345-gpio
+    enum:
+      - brcm,bcm6345-gpio
+      - intel,ixp4xx-expansion-bus-mmio-gpio
+      - ni,169445-nand-gpio
+      - opencores,gpio
+      - wd,mbl-gpio # Western Digital MyBook Live memory-mapped GPIO controller
 
   big-endian: true