arm64: dts: qcom: pm6150: Add label to pwrkey node

arm64: dts: qcom: pm6150: Add label to pwrkey node

Some platforms don't want to use the pmic power key as the power key
event. Add a label so platforms can easily reference and mark this node
as status = "disabled".

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Kiran Gunda <kgunda@codeaurora.org>
Cc: Rajendra Nayak <rnayak@codeaurora.org>
Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20200115025314.3054-1-swboyd@chromium.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>