arm64: dts: rockchip: fix pinmux of UART5 for PX30 Ringneck on Haikou

arm64: dts: rockchip: fix pinmux of UART5 for PX30 Ringneck on Haikou

UART5 uses GPIO0_B5 as UART RTS but muxed in its GPIO function,
therefore UART5 must request this pin to be muxed in that function, so
let's do that.

Fixes: 5963d97aa780 ("arm64: dts: rockchip: add rs485 support on uart5 of px30-ringneck-haikou")
Cc: stable@vger.kernel.org
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Link: https://lore.kernel.org/r/20250225-ringneck-dtbos-v3-2-853a9a6dd597@cherry.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>