Use labels instead of constants for HRAM

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

engine/link/link_trade.asm

@@ -185,10 +185,10 @@ LinkTradeMenu:
 .GetJoypad:
 	push bc
 	push af
-	ld a, [hJoyLast]
+	ldh a, [hJoyLast]
 	and D_PAD
 	ld b, a
-	ld a, [hJoyPressed]
+	ldh a, [hJoyPressed]
 	and BUTTONS
 	or b
 	ld b, a
@@ -201,11 +201,11 @@ LinkTradeMenu:
 .MenuAction:
 	ld hl, w2DMenuFlags2
 	res 7, [hl]
-	ld a, [hBGMapMode]
+	ldh a, [hBGMapMode]
 	push af
 	call .loop
 	pop af
-	ld [hBGMapMode], a
+	ldh [hBGMapMode], a
 	ret
 
 .loop
@@ -228,15 +228,15 @@ LinkTradeMenu:
 	ret
 
 .UpdateBGMapAndOAM:
-	ld a, [hOAMUpdate]
+	ldh a, [hOAMUpdate]
 	push af
 	ld a, $1
-	ld [hOAMUpdate], a
+	ldh [hOAMUpdate], a
 	call WaitBGMap
 	pop af
-	ld [hOAMUpdate], a
+	ldh [hOAMUpdate], a
 	xor a
-	ld [hBGMapMode], a
+	ldh [hBGMapMode], a
 	ret
 
 .loop2

engine/link/time_capsule.asm

@@ -128,7 +128,7 @@ PlaceTradePartnerNamesAndParty:
 	push de
 	push hl
 	ld a, c
-	ld [hProduct], a
+	ldh [hProduct], a
 	call GetPokemonName
 	pop hl
 	call PlaceString