ARM: dts: imx6qdl-tqma6: add ERR006687 hardware workaround for "a" variant

The TQMa6x "a" has a workaround for ERR006687 implemented in hardware.
Add the required pinmuxing and related setup to make use of this.

As board DTS files based on the TQMa6x SoMs will define their own
pinmuxing for the FEC ethernet controller as well, we can't apply this
pin group unconditionally; instead, it is the responsibility of the
board DTs derived from imx6qdl-tqma6a.dtsi to include this group.
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-tqma6a.dtsi

@@ -4,6 +4,12 @@
  * Copyright 2013-2017 Markus Niebel <Markus.Niebel@tq-group.com>
  */
 
+&fec {
+	interrupts-extended = <&gpio1 6 IRQ_TYPE_LEVEL_HIGH>,
+			      <&intc 0 119 IRQ_TYPE_LEVEL_HIGH>;
+	fsl,err006687-workaround-present;
+};
+
 &i2c1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_i2c1>;
@@ -26,3 +32,17 @@ eeprom@50 {
 		pagesize = <32>;
 	};
 };
+
+&iomuxc {
+	/*
+	 * This pinmuxing is required for the ERR006687 workaround. Board
+	 * DTS files that enable the FEC controller with
+	 * fsl,err006687-workaround-present must include this group.
+	 */
+	pinctrl_enet_fix: enetfixgrp {
+		fsl,pins = <
+			/* ENET ping patch */
+			MX6QDL_PAD_GPIO_6__ENET_IRQ 0x000b1
+		>;
+	};
+};