ARM: dts: at91: sama5d2_xplained: enable ADTRG pin

Enable pinctrl for ADTRG pin (PD31) for ADC hardware trigger support.
Signed-off-by: NEugen Hristev <eugen.hristev@microchip.com>
Acked-by: NLudovic Desroches <ludovic.desroches@microchip.com>
Acked-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NNicolas Ferre <nicolas.ferre@microchip.com>

arch/arm/boot/dts/at91-sama5d2_xplained.dts

@@ -309,7 +309,7 @@
 				vddana-supply = <&vdd_3v3_lp_reg>;
 				vref-supply = <&vdd_3v3_lp_reg>;
 				pinctrl-names = "default";
-				pinctrl-0 = <&pinctrl_adc_default>;
+				pinctrl-0 = <&pinctrl_adc_default &pinctrl_adtrg_default>;
 				status = "okay";
 			};
 
@@ -340,6 +340,20 @@
 					bias-disable;
 				};
 
+				/*
+				 * The ADTRG pin can work on any edge type.
+				 * In here it's being pulled up, so need to
+				 * connect it to ground to get an edge e.g.
+				 * Trigger can be configured on falling, rise
+				 * or any edge, and the pull-up can be changed
+				 * to pull-down or left floating according to
+				 * needs.
+				 */
+				pinctrl_adtrg_default: adtrg_default {
+					pinmux = <PIN_PD31__ADTRG>;
+					bias-pull-up;
+				};
+
 				pinctrl_charger_chglev: charger_chglev {
 					pinmux = <PIN_PA12__GPIO>;
 					bias-disable;