ARM: dts: stm32: enable SMC watchdog for STM32MP15 SCMI config

For this configuration, the watchdog (iwdg1) is secured and managed by
OP-TEE. Add an watchdog node with arm,smc-wdt compatible, and disable
iwdg2 node which is then no more used.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>

arch/arm/dts/stm32mp15-scmi-u-boot.dtsi

@@ -21,6 +21,13 @@
 		pinctrl1 = &pinctrl_z;
 	};
 
+	arm_wdt: watchdog {
+		compatible = "arm,smc-wdt";
+		arm,smc-id = <0xbc000000>;
+		timeout-sec = <32>;
+		status = "okay";
+	};
+
 	binman: binman {
 		multiple-images;
 	};
@@ -103,7 +110,7 @@
 };
 
 &iwdg2 {
-	bootph-all;
+	status = "disabled";
 };
 
 /* pre-reloc probe = reserve video frame buffer in video_reserve() */