dt-bindings: ata: fix typo in Allwinner R40 reset specific paragraph

"Property" is misspelled, correct it.

Fixes: caf8975b ("dt-bindings: ata: update ahci_sunxi bindings")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Rob Herring <robh@kernel.org>