Use labels instead of constants for HRAM

Use explicit ldh instruction to access HRAM locations, don't rely on optimizing ld

engine/events/buena_menu.asm

@@ -43,16 +43,16 @@ AskRememberPassword:
 	ret
 
 Buena_ExitMenu:
-	ld a, [hOAMUpdate]
+	ldh a, [hOAMUpdate]
 	push af
 	call ExitMenu
 	call UpdateSprites
 	xor a
-	ld [hOAMUpdate], a
+	ldh [hOAMUpdate], a
 	call DelayFrame
 	ld a, $1
-	ld [hOAMUpdate], a
+	ldh [hOAMUpdate], a
 	call ApplyTilemap
 	pop af
-	ld [hOAMUpdate], a
+	ldh [hOAMUpdate], a
 	ret