Add init function to RGBLight driver struct (#23076)

quantum/rgblight/rgblight_drivers.h

@@ -7,6 +7,7 @@
 #include "color.h"
 
 typedef struct {
+    void (*init)(void);
     void (*setleds)(rgb_led_t *ledarray, uint16_t number_of_leds);
 } rgblight_driver_t;