dt-bindings: serial: lpuart: Drop unsupported RS485 bindings

LPUART driver does not support 'rs485-rts-delay' or
'rs485-rx-during-tx' properties. Remove them.
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-imx@nxp.com
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/20191022044940.15119-1-andrew.smirnov@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/fsl-lpuart.txt

@@ -21,8 +21,7 @@ Required properties:
 Optional properties:
 - dmas: A list of two dma specifiers, one for each entry in dma-names.
 - dma-names: should contain "tx" and "rx".
-- rs485-rts-delay, rs485-rts-active-low, rs485-rx-during-tx,
-  linux,rs485-enabled-at-boot-time: see rs485.txt
+- rs485-rts-active-low, linux,rs485-enabled-at-boot-time: see rs485.txt
 
 Note: Optional properties for DMA support. Write them both or both not.