dt-bindings: backlight: lm3630a: Fix missing include

Example failed to compile due to undefined GPIO_ACTIVE_HIGH
fix that by adding the needed #include to the exammple.

Signed-off-by: Andreas Kemnade <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml

···
 
 examples:
   - |
+    #include <dt-bindings/gpio/gpio.h>
     i2c {
         #address-cells = <1>;
         #size-cells = <0>;