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

[ Upstream commit 403e97d6 ]

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.it
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>