dt-bindings: serial: 8250_omap: drop rs485 properties

The binding references rs485 schema, so there is no need to list its
properties.  Simplify a bit by removing unneeded entries.
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: NRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230124091916.45054-4-krzysztof.kozlowski@linaro.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -70,11 +70,6 @@ properties:
   dsr-gpios: true
   rng-gpios: true
   dcd-gpios: true
-  rs485-rts-delay: true
-  rs485-rts-active-low: true
-  rs485-rx-during-tx: true
-  rs485-rts-active-high: true
-  linux,rs485-enabled-at-boot-time: true
   rts-gpio: true
   power-domains: true
   clock-frequency: true