docs: dt: fix references to ap806-system-controller.txt

ap806-system-controller.txt was renamed to ap80x-system-controller.txt.

Update its references accordingly.

Fixes: 2537831bbc19 ("dt-bindings: ap80x: replace AP806 with AP80x")
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Acked-by: Bartosz Golaszewski <[e-mail]>
Reviewed-by: Miquel Raynal <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/gpio/gpio-mvebu.txt

···
 
     "marvell,armada-8k-gpio" should be used for the Armada 7K and 8K
     SoCs (either from AP or CP), see
-    Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt
+    Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt
     for specific details about the offset property.
 
 - reg: Address and length of the register set for the device. Only one

Documentation/devicetree/bindings/thermal/armada-thermal.txt

···
 
 Note: these bindings are deprecated for AP806/CP110 and should instead
 follow the rules described in:
-Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt
+Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt
 Documentation/devicetree/bindings/arm/marvell/cp110-system-controller.txt
 
 - reg: Device's register space.