ARM: dts: imx50-kobo-aura: Enable eKTF2132 touchscreen

The Kobo Aura has an eKTF2132 touchscreen controller.

Although the vendor kernel toggles a reset pin (GPIO5-12) during the
startup sequence, the touchscreen works without it.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx50-kobo-aura.dts

@@ -6,6 +6,7 @@
 /dts-v1/;
 #include "imx50.dtsi"
 #include <dt-bindings/input/input.h>
+#include <dt-bindings/interrupt-controller/irq.h>
 
 / {
 	model = "Kobo Aura (N514)";
@@ -119,7 +120,14 @@ &i2c1 {
 	pinctrl-0 = <&pinctrl_i2c1>;
 	status = "okay";
 
-	/* TODO: ektf2132 touch controller at 0x15 */
+	touchscreen@15 {
+		reg = <0x15>;
+		compatible = "elan,ektf2132";
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_ts>;
+		power-gpios = <&gpio4 9 GPIO_ACTIVE_HIGH>;
+		interrupts-extended = <&gpio5 13 IRQ_TYPE_EDGE_FALLING>;
+	};
 };
 
 &i2c2 {
@@ -225,6 +233,13 @@ MX50_PAD_SD3_D7__ESDHC3_DAT7		0x1d4
 		>;
 	};
 
+	pinctrl_ts: tsgrp {
+		fsl,pins = <
+			MX50_PAD_CSPI_MOSI__GPIO4_9		0x0
+			MX50_PAD_SD2_D5__GPIO5_13		0x0
+		>;
+	};
+
 	pinctrl_uart2: uart2grp {
 		fsl,pins = <
 			MX50_PAD_UART2_TXD__UART2_TXD_MUX	0x1e4