Solved a bunch of -Wall errors on modern

src/trainer_hill.c

@@ -571,7 +571,7 @@ static void IsTrainerHillChallengeActive(void)
         gSpecialVar_Result = TRUE;
 }
 
-static void TrainerHillDummy_Unused(void)
+static void UNUSED TrainerHillDummy_Unused(void)
 {
 
 }
@@ -769,8 +769,7 @@ u8 GetCurrentTrainerHillMapId(void)
     return mapId;
 }
 
-// Unused
-static bool32 OnTrainerHillRoof(void)
+static bool32 UNUSED OnTrainerHillRoof(void)
 {
     bool32 onRoof;