Use FADE_TO_BLACK define in other files

src/credits.c

@@ -15,6 +15,7 @@
 #include "sound.h"
 #include "constants/species.h"
 #include "constants/maps.h"
+#include "constants/field_weather.h"
 
 #if defined(FIRERED)
 #define TITLE_TEXT gString_PokemonFireRed_Staff
@@ -918,7 +919,7 @@ static s32 RollCredits(void)
             case CREDITSSCRCMD_MON:
                 sCreditsMgr->mainseqno = CREDITSSCENE_MON_DESTROY_ASSETS;
                 sCreditsMgr->whichMon = sCreditsScript[sCreditsMgr->scrcmdidx].param;
-                FadeScreen(1, 0);
+                FadeScreen(FADE_TO_BLACK, 0);
                 break;
             case CREDITSSCRCMD_THEENDGFX:
                 sCreditsMgr->mainseqno = CREDITSSCENE_THEEND_DESTROY_ASSETS;