dt-bindings: ata: ahci-platform: add missing iommus property

fix dtbs_check errors in following files:

arch/arm64/boot/dts/marvell/armada-7040-db.dtb: sata@540000:
arch/arm64/boot/dts/marvell/armada-8040-clearfog-gt-8k.dtb: sata@540000:
arch/arm64/boot/dts/marvell/armada-8040-db.dtb: sata@540000:
arch/arm64/boot/dts/marvell/armada-8040-mcbin.dtb: sata@540000:
arch/arm64/boot/dts/marvell/armada-8040-puzzle-m801.dtb: sata@540000:
  Unevaluated properties are not allowed ('iommus' was unexpected)

Signed-off-by: Frank Wunderlich <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Acked-by: Conor Dooley <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Niklas Cassel <[email protected]>

Author: frank-w

Documentation/devicetree/bindings/ata/ahci-platform.yaml

@@ -84,6 +84,9 @@ properties:
     minItems: 1
     maxItems: 3
 
+  iommus:
+    maxItems: 1
+
 patternProperties:
   "^sata-port@[0-9a-f]+$":
     $ref: /schemas/ata/ahci-common.yaml#/$defs/ahci-port