arm64: dts: imx8mq-librem5-r3.dtsi: describe selfie cam XSHUTDOWN pin

The r3 and later revisions of the Librem 5 phone include an additional switch
to control the hi846 XSHUTDOWN pin. Describe it.
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dtsi

@@ -27,6 +27,19 @@ &bq25895 {
 	ti,termination-current = <144000>;  /* uA */
 };
 
+&camera_front {
+	pinctrl-0 = <&pinctrl_csi1>, <&pinctrl_r3_camera_pwr>;
+	shutdown-gpios = <&gpio5 4 GPIO_ACTIVE_LOW>;
+};
+
+&iomuxc {
+	pinctrl_r3_camera_pwr: r3camerapwrgrp {
+		fsl,pins = <
+			MX8MQ_IOMUXC_SPDIF_RX_GPIO5_IO4		0x83
+		>;
+	};
+};
+
 &proximity {
 	proximity-near-level = <25>;
 };