dt-bindings: serial: fsl-imx-uart: Remove 'fsl,irda-mode' property

'fsl,irda-mode' property has been removed since commit afe9cbb1
("serial: imx: drop support for IRDA"), so remove it from the binding
document.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/fsl-imx-uart.txt

@@ -6,7 +6,6 @@ Required properties:
 - interrupts : Should contain uart interrupt
 
 Optional properties:
-- fsl,irda-mode : Indicate the uart supports irda mode
 - fsl,dte-mode : Indicate the uart works in DTE mode. The uart works
                   in DCE mode by default.
 - rs485-rts-delay, rs485-rx-during-tx, linux,rs485-enabled-at-boot-time: see rs485.txt