arm64: dts: qcom: qrb5165-rb5: declare tri-led user leds

Qualcomm RB5 platform uses Light Pulse Generator tri-led block to drive
three green leds. Add device nodes defining those leds.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220505145102.1432670-4-dmitry.baryshkov@linaro.org