dt-bindings: serial: rs485: Add rs485-rts-active-high

Add rs485-rts-active-high property, this is a legacy property
used by 8250_omap.

This fixes the following make dt_binding_check warning:

Documentation/devicetree/bindings/serial/8250_omap.yaml:
rs485-rts-active-high: missing type definition

Reported-by: Geert Uytterhoeven <[email protected]>
Closes: https://lore.kernel.org/all/CAMuHMdUkPiA=o_QLyuwsTYW7y1ksCjHAqyNSHFx2QZ-dP-HGsQ@mail.gmail.com/
Fixes: 403e97d ("dt-bindings: serial: 8250_omap: add rs485-rts-active-high")
Cc: stable <[email protected]>
Signed-off-by: Francesco Dolcini <[email protected]>
Reviewed-by: Krzysztof Kozlowski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: dolcini

Documentation/devicetree/bindings/serial/rs485.yaml

@@ -29,6 +29,10 @@ properties:
           default: 0
           maximum: 100
 
+  rs485-rts-active-high:
+    description: drive RTS high when sending (this is the default).
+    $ref: /schemas/types.yaml#/definitions/flag
+
   rs485-rts-active-low:
     description: drive RTS low when sending (default is high).
     $ref: /schemas/types.yaml#/definitions/flag