dt-bindings: serial: 8250_omap: add rs485-rts-active-high

Add rs485-rts-active-high property, this was removed by mistake.
In general we just use rs485-rts-active-low property, however the OMAP
UART for legacy reason uses the -high one.

Fixes: 767d3467 ("dt-bindings: serial: 8250_omap: drop rs485 properties")
Closes: https://lore.kernel.org/all/ZGefR4mTHHo1iQ7H@francesco-nb.int.toradex.com/Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230531111038.6302-1-francesco@dolcini.itSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/8250_omap.yaml

@@ -70,6 +70,7 @@ properties:
   dsr-gpios: true
   rng-gpios: true
   dcd-gpios: true
+  rs485-rts-active-high: true
   rts-gpio: true
   power-domains: true
   clock-frequency: true