arm64: dts: qcom: sc7180-trogdor: add "pen-insert" label for trogdor

Add a label to the "pen-insert" node in sc7180-trogdor.dtsi
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Terry Hsiao <terry_hsiao@compal.corp-partner.google.com>
Link: https://lore.kernel.org/r/20201116083014.547-1-terry_hsiao@compal.corp-partner.google.comSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi

@@ -218,7 +218,7 @@ gpio_keys: gpio-keys {
 		pinctrl-names = "default";
 		pinctrl-0 = <&pen_pdct_l>;
 
-		pen-insert {
+		pen_insert: pen-insert {
 			label = "Pen Insert";
 
 			/* Insert = low, eject = high */