arm64: dts: qcom: sm8550: add UART14 nodes

Add the Geni High Speed UART QUP instance 2 element 6
node and associated default pinctrl.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20230911-topic-sm8550-upstream-bt-v4-1-a5a428c77418@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>