Convert eeconfig_init_kb implementations to config (#24087)

keyboards/keebio/sinc/rev1/keyboard.json

@@ -57,6 +57,9 @@
         ]
     },
     "backlight": {
+        "default": {
+            "brightness": 3
+        },
         "pin": "B5"
     },
     "rgblight": {

keyboards/keebio/sinc/rev2/keyboard.json

@@ -57,6 +57,9 @@
         ]
     },
     "backlight": {
+        "default": {
+            "brightness": 3
+        },
         "pin": "B5"
     },
     "rgblight": {

keyboards/keebio/sinc/sinc.c

@@ -28,15 +28,6 @@ bool led_update_kb(led_t led_state) {
 }
 #endif
 
-void eeconfig_init_kb(void) {
-#ifdef BACKLIGHT_ENABLE
-    backlight_enable();
-    backlight_level(3);
-#endif
-    eeconfig_update_kb(0);
-    eeconfig_init_user();
-}
-
 #ifdef ENCODER_ENABLE
 bool encoder_update_kb(uint8_t index, bool clockwise) {
     if (!encoder_update_user(index, clockwise)) { return false; }