imx: imx8mn-kontron-n801x: enable pinctrl_wdog in SPL

Mark pinctrl_wdog as u-boot,dm-spl to clean up board code,

The set_wdog_reset() function is not necessary as this is handled by
the imx_watchdog.c driver due to the 'fsl,ext-reset-output' property
being set.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
diff --git a/arch/arm/dts/imx8mm-kontron-n801x-u-boot.dtsi b/arch/arm/dts/imx8mm-kontron-n801x-u-boot.dtsi
index 22d18e6..6882513 100644
--- a/arch/arm/dts/imx8mm-kontron-n801x-u-boot.dtsi
+++ b/arch/arm/dts/imx8mm-kontron-n801x-u-boot.dtsi
@@ -126,3 +126,7 @@
 &wdog1 {
 	u-boot,dm-spl;
 };
+
+&pinctrl_wdog {
+	u-boot,dm-spl;
+};