MLK-12126 ARM: dts: imx6/imx7d: correct wdog pinctrl setting

MLK-12126 ARM: dts: imx6/imx7d: correct wdog pinctrl setting

We move WDOG_B pinctrl setting from pinctrl_hog to wdog driver, so need to
remove the original setting in pinctl_hog device node, otherwise the below
warning message will be caught:

[    1.284161] imx6ul-pinctrl 20e0000.iomuxc: pin MX6UL_PAD_LCD_RESET already requested by 20e0000.iomuxc; cannot claim for 20bc000.wdog
[    1.294990] imx6ul-pinctrl 20e0000.iomuxc: pin-69 (20bc000.wdog) status -22
[    1.300689] imx6ul-pinctrl 20e0000.iomuxc: could not request pin 69 (MX6UL_PAD_LCD_RESET) from group wdoggrp  on device 20e0000.iomuxc
[    1.311550] imx2-wdt 20bc000.wdog: Error applying setting, reverse things back

Signed-off-by: Robin Gong <b38343@freescale.com>