ARM: ux500: Apply ab8500-debug node do the db8500 DT structure

This node has no properties. It merely allows probing of the
ab8500-debugfs driver during Device Tree initialisation.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

arch/arm/boot/dts/db8500.dtsi

@@ -357,6 +357,10 @@ ab8500-pwm {
 					compatible = "stericsson,ab8500-pwm";
 				};
 
+				ab8500-debugfs {
+					compatible = "stericsson,ab8500-debug";
+				};
+
 				ab8500-regulators {
 					compatible = "stericsson,ab8500-regulator";