kconfig: error out when seeing recursive dependency

Originally, recursive dependency was a fatal error for Kconfig
because Kconfig cannot compute symbol values in such a situation.

Commit d595cea62403 ("kconfig: print more info when we see a recursive
dependency") changed it to a warning, which I guess was not intentional.

Get it back to an error again.

Also, rename the unit test directory "warn_recursive_dep" to
"err_recursive_dep" so that it matches to the behavior.

Signed-off-by: Masahiro Yamada <[e-mail]>
Tested-by: Dirk Gouders <[e-mail]>

scripts/kconfig/symbol.c

···
 		sym->flags &= ~SYMBOL_CHECK;
 	}
 
-	if (sym2 && sym2 == sym)
-		sym2 = NULL;
-
 	return sym2;
 }
 

scripts/kconfig/tests/err_recursive_dep/__init__.py

···
+# SPDX-License-Identifier: GPL-2.0
+"""
+Detect recursive dependency error.
+
+Recursive dependency should be treated as an error.
+"""
+
+def test(conf):
+    assert conf.oldaskconfig() == 1
+    assert conf.stderr_contains('expected_stderr')

scripts/kconfig/tests/warn_recursive_dep/__init__.py

···
-"""
-Warn recursive inclusion.
-
-Recursive dependency should be warned.
-"""
-
-def test(conf):
-    assert conf.oldaskconfig() == 0
-    assert conf.stderr_contains('expected_stderr')