arm64: dts: qcom: sm8150: simplify references to pwrkey and resin

Since commit d0a6ce59 ("arm64: dts: qcom: sm8150: Add support for
SONY Xperia 1 / 5 (Kumano platform)"), we can directly refer to pwrkey
and resin by their new labels, respectively pon_pwrkey and pon_resin.

Simplify microsof surface duo DTS by utilizing the new labels.

Signed-off-by: Felipe Balbi <felipe.balbi@microsoft.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211217124546.1192281-1-balbi@kernel.org