port HasNoMonsToSwitch fakematch fix (from #1181)

src/battle_util.c

@@ -1634,16 +1634,8 @@ bool8 HasNoMonsToSwitch(u8 battler, u8 partyIdBattlerOn1, u8 partyIdBattlerOn2)
             }
             else
             {
-                // FIXME: Compiler insists on moving r4 into r1 before doing the eor.
-                #ifndef NONMATCHING
-                    register u32 var asm("r1");
-                #else
-                    u32 var;
-                #endif // NONMATCHING
-
                 party = gEnemyParty;
-                var = battler ^ BIT_SIDE;
-                if (var == 0)
+                if (battler == 1)
                     id1 = 0;
                 else
                     id1 = 1;