rgblight split transfer non-eeprom config (#5396)

* Make rgblight_update_dword not update eeprom (we already have
eeconfig_update_rgblight for that).

Make split i2c keyboards transfer active rgblight config rather than
eeprom saved version of rgblight config, enabling runtime changes
that aren't persisted to eeprom.

* prev_level and prev_rgb only store successfully transmitted values

quantum/api.c

@@ -67,7 +67,7 @@ void process_api(uint16_t length, uint8_t * data) {
                 case DT_RGBLIGHT: {
                     #ifdef RGBLIGHT_ENABLE
                         uint32_t rgblight = bytes_to_dword(data, 2);
-                        rgblight_update_dword(rgblight);
+                        eeconfig_update_rgblight(rgblight);
                     #endif
                     break;
                 }