arm64: dts: imx8mm-data-modul: Rename /watchdog-gpio to plain /watchdog

The DT bindings checker is confused by the -gpio node suffix,
drop it to fix the following warning:
"
imx8mm-data-modul-edm-sbc.dtb: /: watchdog-gpio: {'pinctrl-names': ['default'], 'pinctrl-0': [[104]], 'compatible': ['linux,wdt-gpio'], 'always-enabled': True, 'gpios': [[45, 8, 0]], 'hw_algo': ['level'], 'hw_margin_ms': [[1500]], 'status': ['disabled']} is not of type 'array'
"
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-data-modul-edm-sbc.dts

@@ -83,7 +83,7 @@ reg_usdhc2_vcc: regulator-usdhc2-vcc {
 		enable-active-high;
 	};
 
-	watchdog-gpio {
+	watchdog {
 		/* TPS3813 */
 		pinctrl-names = "default";
 		pinctrl-0 = <&pinctrl_watchdog_gpio>;