powerpc: p2020: Rename wdt@ nodes to watchdog@

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

Signed-off-by: J. Neuschäfer <[e-mail]>
Reviewed-by: Christophe Leroy <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/boot/dts/fsl/ge_imp3a.dts

···
 			gpio-controller;
 		};
 
-		wdt@4,800 {
+		watchdog@4,800 {
 			compatible = "ge,imp3a-fpga-wdt", "gef,fpga-wdt-1.00",
 				"gef,fpga-wdt";
 			reg = <0x4 0x800 0x8>;
···
 		};
 
 		/* Second watchdog available, driver currently supports one.
-		wdt@4,808 {
+		watchdog@4,808 {
 			compatible = "gef,imp3a-fpga-wdt", "gef,fpga-wdt-1.00",
 				"gef,fpga-wdt";
 			reg = <0x4 0x808 0x8>;