Merged Fliphalf, now defined in config, added OLED

Can now use the following in the keymap config.h to call the flipped matrix

```
#define FLIPHALF
```

keyboards/lets_split/rev2/rev2.c

@@ -5,6 +5,13 @@
     float tone_goodbye[][2] = SONG(GOODBYE_SOUND);
 #endif
 
+#ifdef SSD1306OLED
+void led_set_kb(uint8_t usb_led) {
+    // put your keyboard LED indicator (ex: Caps Lock LED) toggling code here
+    led_set_user(usb_led);
+}
+#endif
+
 void matrix_init_kb(void) {
 
     #ifdef AUDIO_ENABLE
@@ -30,3 +37,4 @@ void shutdown_user(void) {
 	stop_all_notes();
     #endif
 }
+