FIR2IR: fix origin calculation for explicit inc/dec calls

compiler/testData/ir/irText/firProblems/explicitIncrement.ir.txt

@@ -0,0 +1,16 @@
+FILE fqName:<root> fileName:/explicitIncrement.kt
+  FUN name:foo visibility:public modality:FINAL <> () returnType:kotlin.Unit
+    BLOCK_BODY
+      VAR name:i type:kotlin.Int [var]
+        CONST Int type=kotlin.Int value=1
+      WHILE label=null origin=WHILE_LOOP
+        condition: CALL 'public final fun less (arg0: kotlin.Int, arg1: kotlin.Int): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=LT
+          arg0: GET_VAR 'var i: kotlin.Int declared in <root>.foo' type=kotlin.Int origin=null
+          arg1: CONST Int type=kotlin.Int value=10
+        body: BLOCK type=kotlin.Unit origin=null
+          CALL 'public final fun bar (): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          SET_VAR 'var i: kotlin.Int declared in <root>.foo' type=kotlin.Unit origin=EQ
+            CALL 'public final fun inc (): kotlin.Int declared in kotlin.Int' type=kotlin.Int origin=null
+              $this: GET_VAR 'var i: kotlin.Int declared in <root>.foo' type=kotlin.Int origin=null
+  FUN name:bar visibility:public modality:FINAL <> () returnType:kotlin.Unit
+    BLOCK_BODY

compiler/testData/ir/irText/firProblems/explicitIncrement.kt

@@ -0,0 +1,10 @@
+// FIR_IDENTICAL
+fun foo() {
+    var i = 1
+    while (i < 10) {
+        bar()
+        i = i.inc()
+    }
+}
+
+fun bar() {}

compiler/testData/ir/irText/firProblems/explicitIncrement.kt.txt

@@ -0,0 +1,11 @@
+fun foo() {
+  var i: Int = 1
+  while (less(arg0 = i, arg1 = 10)) { // BLOCK
+    bar()
+    i = i.inc()
+  }
+}
+
+fun bar() {
+}
+

compiler/testData/ir/irText/firProblems/explicitIncrement.sig.kt.txt

@@ -0,0 +1,10 @@
+// CHECK:
+//   Mangled name: #bar(){}
+//   Public signature: /bar|496682602797471549[0]
+fun bar(): Unit
+
+// CHECK:
+//   Mangled name: #foo(){}
+//   Public signature: /foo|-1041209573719867811[0]
+fun foo(): Unit
+