imx: imx8mp_rsb7320a1: enable wdog driver model in SPL

Mark wdog1/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>
diff --git a/arch/arm/dts/imx8mp-rsb3720-a1-u-boot.dtsi b/arch/arm/dts/imx8mp-rsb3720-a1-u-boot.dtsi
index 2848b24..4419967 100644
--- a/arch/arm/dts/imx8mp-rsb3720-a1-u-boot.dtsi
+++ b/arch/arm/dts/imx8mp-rsb3720-a1-u-boot.dtsi
@@ -89,6 +89,14 @@
 	u-boot,dm-spl;
 };
 
+&wdog1 {
+	u-boot,dm-spl;
+};
+
+&pinctrl_wdog {
+	u-boot,dm-spl;
+};
+
 &pinctrl_i2c1 {
 	u-boot,dm-spl;
 };