powerpc: 512x: Rename wdt@ node to watchdog@

The watchdog.yaml schema prescribes a node name of "timer" or "watchdog"
rather than the abbreviation "wdt".

Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250418-watchdog-v1-1-987ff2046272@posteo.net

Author: neuschaefer

arch/powerpc/boot/dts/mpc5121.dtsi

@@ -112,7 +112,7 @@
 		};
 
 		/* Watchdog timer */
-		wdt@900 {
+		watchdog@900 {
 			compatible = "fsl,mpc5121-wdt";
 			reg = <0x900 0x100>;
 		};