arm64: dts: qcom: qcs404: Specify pinctrl state for UART

BLSP1 UART2 is used as debug uart on the EVB development board, define
pinmux state for the UART in the platform dtsi and pinconf state for it
in the board dts.

Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>