Fix Knock Off, add config

Added a config for Knock Off's damage boost. Also fixed the conditions it checks to do bonus damage.

include/constants/battle_config.h

@@ -114,6 +114,7 @@
 #define B_PAYBACK_SWITCH_BOOST      GEN_7 // In Gen5+, if the opponent switches out, Payback's damage will no longer be doubled.
 #define B_HIDDEN_POWER_DMG          GEN_7 // In Gen6+, Hidden Power's base power was set to always be 60. Before, it was determined by the mon's IVs.
 #define B_ROUGH_SKIN_DMG            GEN_7 // In Gen4+, Rough Skin contact damage is 1/8th of max HP instead of 1/16th. This will also affect Iron Barbs.
+#define B_KNOCK_OFF_DMG             GEN_8 // In Gen6+, Knock Off deals 50% more damage when knocking off an item
 
 // Type settings
 #define B_GHOSTS_ESCAPE             GEN_7 // In Gen6+, abilities like Shadow Tag or moves like Mean Look fail on Ghost-type Pokémon. They can also escape any Wild Battle.

src/battle_util.c

@@ -8191,8 +8191,11 @@ static u32 CalcMoveBasePowerAfterModifiers(u16 move, u8 battlerAtk, u8 battlerDe
             MulModifier(&modifier, UQ_4_12(0.5));
         break;
     case EFFECT_KNOCK_OFF:
-        if (gBattleMons[battlerDef].item != ITEM_NONE && GetBattlerAbility(battlerDef) != ABILITY_STICKY_HOLD)
+        #if B_KNOCK_OFF_DMG >= GEN_6
+        if (gBattleMons[battlerDef].item != ITEM_NONE
+            && CanBattlerGetOrLoseItem(battlerDef, gBattleMons[battlerDef].item))
             MulModifier(&modifier, UQ_4_12(1.5));
+        #endif
         break;
     }