For namespaces with multiple files keep 'Compiled from' information empty

compiler/testData/codegen/sourceInfo/foo1.kt

@@ -0,0 +1,5 @@
+package foo;
+
+fun box() = {
+  1
+}

compiler/testData/codegen/sourceInfo/foo2.kt

@@ -0,0 +1,5 @@
+package foo;
+
+fun box2() = {
+  1
+}

compiler/testData/codegen/sourceInfo/singleClass.kt

@@ -0,0 +1,4 @@
+class SingleClass {
+
+
+}