ARM: dts: imx6qdl-wandboard-revd1: Remove PAD_GPIO_6 from enetgrp

Since commit 8ad2d1dc ("ARM: dts: imx6qdl-wandboard: Add OV5645 camera
support") the PAD_GPIO_6 is used for providing the camera sensor clock.

Remove it from the enetgrp to fix the following IOMXU conflict:

[    9.972414] imx6q-pinctrl 20e0000.pinctrl: pin MX6Q_PAD_GPIO_6 already requested by 2188000.ethernet; cannot claim for 1-003c
[    9.983857] imx6q-pinctrl 20e0000.pinctrl: pin-140 (1-003c) status -22
[    9.990514] imx6q-pinctrl 20e0000.pinctrl: could not request pin 140 (MX6Q_PAD_GPIO_6) from group ov5645grp  on device 20e0000.pinctrl

Fixes: 8ad2d1dc ("ARM: dts: imx6qdl-wandboard: Add OV5645 camera support")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>