Use labels instead of constants for HRAM

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

engine/events/battle_tower/load_trainer.asm

@@ -1,8 +1,8 @@
 Function_LoadOpponentTrainerAndPokemons:
-	ld a, [rSVBK]
+	ldh a, [rSVBK]
 	push af
 	ld a, BANK(wBT_OTTrainer)
-	ld [rSVBK], a
+	ldh [rSVBK], a
 
 	; Fill wBT_OTTrainer with zeros
 	xor a
@@ -19,11 +19,11 @@ Function_LoadOpponentTrainerAndPokemons:
 	; Set wBT_OTTrainer as start address to write the following data to
 	ld de, wBT_OTTrainer
 
-	ld a, [hRandomAdd]
+	ldh a, [hRandomAdd]
 	ld b, a
 .resample ; loop to find a random trainer
 	call Random
-	ld a, [hRandomAdd]
+	ldh a, [hRandomAdd]
 	add b
 	ld b, a ; b contains the nr of the trainer
 if DEF(_CRYSTAL11)
@@ -87,7 +87,7 @@ endc
 	jr nz, .copy_bt_trainer_data_loop
 
 	pop af
-	ld [rSVBK], a
+	ldh [rSVBK], a
 
 	ret
 
@@ -107,11 +107,11 @@ Function_LoadRandomBattleTowerMon:
 	ld bc, BattleTowerMons2 - BattleTowerMons1 ; size of one level group
 	call AddNTimes
 
-	ld a, [hRandomAdd]
+	ldh a, [hRandomAdd]
 	ld b, a
 .resample
 	call Random
-	ld a, [hRandomAdd]
+	ldh a, [hRandomAdd]
 	add b
 	ld b, a
 	maskbits BATTLETOWER_NUM_UNIQUE_MON