Identify some wMenuJoypad-related button constants

engine/events/buena.asm

@@ -234,7 +234,7 @@ Buena_PrizeMenu:
 	ld a, [wMenuCursorY]
 	ld [wMenuSelection], a
 	ld a, [wMenuJoypad]
-	cp $2
+	cp B_BUTTON
 	jr z, .cancel
 	ld a, c
 	and a

engine/items/tmhm.asm

@@ -290,7 +290,7 @@ TMHM_CheckHoveringOverCancel:
 TMHM_ExitPack:
 	call TMHM_PlaySFX_ReadText2
 _TMHM_ExitPack:
-	ld a, $2
+	ld a, B_BUTTON
 	ld [wMenuJoypad], a
 	and a
 	ret

engine/overworld/decorations.asm

@@ -376,7 +376,7 @@ PopulateDecoCategoryMenu:
 	ld [wMenuScrollPosition], a
 	call ScrollingMenu
 	ld a, [wMenuJoypad]
-	cp 2
+	cp B_BUTTON
 	jr z, .no_action_2
 	call DoDecorationAction2