arm64: dts: qcom: sm6350-lena: Flatten gpio-keys pinctrl state

Pinctrl states typically collate multiple related pins.  In the case of
gpio-keys there's no hardware-defined relation at all except all pins
representing a key; and especially on Sony's lena board there's only one
pin regardless. Flatten it similar to other boards [1].

As a drive-by fix, clean up the label string.

[1]: https://lore.kernel.org/linux-arm-msm/11174eb6-0a9d-7df1-6f06-da4010f76453@linaro.org/

Fixes: 2b8bbe98 ("arm64: dts: qcom: sm6350-lena: Include pm6350 and configure buttons")
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221222215906.324092-1-marijn.suijten@somainline.org

arch/arm64/boot/dts/qcom/sm6350-sony-xperia-lena-pdx213.dts

@@ -35,10 +35,10 @@ framebuffer: framebuffer@a0000000 {
 	gpio-keys {
 		compatible = "gpio-keys";
 		pinctrl-names = "default";
-		pinctrl-0 = <&gpio_keys_state>;
+		pinctrl-0 = <&vol_down_n>;
 
 		key-volume-down {
-			label = "volume_down";
+			label = "Volume Down";
 			linux,code = <KEY_VOLUMEDOWN>;
 			gpios = <&pm6350_gpios 2 GPIO_ACTIVE_LOW>;
 		};
@@ -305,14 +305,12 @@ touchscreen@48 {
 };
 
 &pm6350_gpios {
-	gpio_keys_state: gpio-keys-state {
-		key-volume-down-pins {
-			pins = "gpio2";
-			function = PMIC_GPIO_FUNC_NORMAL;
-			power-source = <0>;
-			bias-disable;
-			input-enable;
-		};
+	vol_down_n: vol-down-n-state {
+		pins = "gpio2";
+		function = PMIC_GPIO_FUNC_NORMAL;
+		power-source = <0>;
+		bias-disable;
+		input-enable;
 	};
 };