riscv: dts: sifive: "fix" pmic watchdog node name

After converting the pmic watchdog binding to yaml, dtbs_check complains
that the node name doesn't match the binding. "Fix" it.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220606201343.514391-5-mail@conchuod.ieSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts

@@ -90,7 +90,7 @@ rtc {
 			compatible = "dlg,da9063-rtc";
 		};
 
-		wdt {
+		watchdog {
 			compatible = "dlg,da9063-watchdog";
 		};