dt-bindings: atmel-nand: add microchip,sam9x60-pmecc

Add microchip,sam9x60-pmecc to DT bindings documentation.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1578673089-3484-9-git-send-email-claudiu.beznea@microchip.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/mtd/atmel-nand.txt

@@ -57,6 +57,7 @@ Required properties:
 	"atmel,at91sam9g45-pmecc"
 	"atmel,sama5d4-pmecc"
 	"atmel,sama5d2-pmecc"
+	"microchip,sam9x60-pmecc"
 - reg: should contain 2 register ranges. The first one is pointing to the PMECC
        block, and the second one to the PMECC_ERRLOC block.