[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/smartCasts/loops/ifInsideDoWhile.fir.kt

@@ -0,0 +1,9 @@
+public fun foo(p: String?, y: String?): Int {
+    do {
+        // After the check, smart cast should work
+        if (y == null) break
+        y.length
+        p!!.length
+    } while (true)
+    return y?.length ?: -1
+}