ARM: dts: s3c24xx: align PWM/timer node name with dtschema

Although PWM is used on S3C24xx as clocksource/timer, the dtschema
expects the node to be named in certain format:

  timer@51000000: $nodename:0: 'timer@51000000' does not match '^pwm(@.*|-[0-9a-f])*$'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200907183313.29234-10-krzk@kernel.org

arch/arm/boot/dts/s3c24xx.dtsi

@@ -39,7 +39,7 @@ wakeup-interrupt-controller {
 		};
 	};
 
-	timer: timer@51000000 {
+	timer: pwm@51000000 {
 		compatible = "samsung,s3c2410-pwm";
 		reg = <0x51000000 0x1000>;
 		interrupts = <0 0 10 3>, <0 0 11 3>, <0 0 12 3>, <0 0 13 3>, <0 0 14 3>;