Fix primitive types mapping

Use boxed version if type was enhaced to not-nullable

compiler/testData/codegen/box/platformTypes/primitives/identityEquals.kt

@@ -3,7 +3,7 @@ fun box(): String {
     l.add(1000)
 
     val x = l[0] === 1000
-    if (!x) return "Fail: $x"
+    if (x) return "Fail: $x"
     val x1 = l[0] === 1
     if (x1) return "Fail 1: $x"
     val x2 = l[0] === l[0]