arm64: dts: qcom: sdm845-tama: Set serial indices and stdout-path

UART6 is used for debug (routed via uSD pins) and UART9 is connected
to the bluetooth chip.

Set indexed aliases to make the GENI UART driver happy and route serial
traffic through the debug uart by default.

Fixes: 30a7f99b ("arm64: dts: qcom: Add support for SONY Xperia XZ2 / XZ2C / XZ3 (Tama platform)")
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Link: https://lore.kernel.org/r/20230627-topic-tama_uart-v1-1-0fa790248db8@linaro.org


Signed-off-by: Bjorn Andersson <andersson@kernel.org>