arm64: dts: qcom: ipq5424: Describe the 4-wire UART SE

arm64: dts: qcom: ipq5424: Describe the 4-wire UART SE

QUPv3 in IPQ5424 consists of six Serial Engines (SEs). Describe the
first SE, which supports a 4-wire UART configuration suitable for
applications such as HS-UART.

Note that the required initialization for this SE is not handled by the
bootloader. Therefore, add the SE node in the device tree but keep it
reserved. Enable it once Linux gains support for configuring the SE,
allowing to use in relevant RDPs.

Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250812-ipq5424_hsuart-v4-1-f1faa7704ea9@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>