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 <frank-w@public-files.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20241109094623.37518-4-linux@fw-web.de


Signed-off-by: Niklas Cassel <cassel@kernel.org>