More minor isolated fixes (#1258)

* Fix reversed array access in z_boss_dodongo.c

* Remove useless return in z_en_encount2.c

* Remove some redundant externs or declarations

* Move some undefs to be performed as early as possible

* AudioOcarina_ResetStaffs -> AudioOcarina_ResetStaves

The plural appears to be staves for the music term

* Remove some uses of UNK_PTR

* Use NULL for pointers set to 0 in z_game_dlftbls.c

* Remove useless !! in z_en_tk.c

* Revert "AudioOcarina_ResetStaffs -> AudioOcarina_ResetStaves"

This reverts commit 1b7fe62408.

* Remove more redundant externs from PR suggestion

src/overlays/actors/ovl_En_Encount2/z_en_encount2.c

@@ -111,7 +111,6 @@ void EnEncount2_Wait(EnEncount2* this, PlayState* play) {
             }
             break;
     }
-    return;
 }
 
 void EnEncount2_SpawnRocks(EnEncount2* this, PlayState* play) {