common: Move hang() to the same header as panic()

At present panic() is in the vsprintf.h header file. That does not seem
like an obvious choice for hang(), even though it relates to panic(). So
let's put hang() in its own header.

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Migrate a few more files]
Signed-off-by: Tom Rini <trini@konsulko.com>

include/hang.h

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * (C) Copyright 2000-2009
+ * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+ */
+
+#ifndef __HANG_H
+#define __HANG_H
+
+#ifndef __ASSEMBLY__
+/**
+ * hang() - Print a message and stop execution
+ *
+ * This shows a 'hang' message where possible and then goes into an infinite
+ * loop. This is called by panic() if CONFIG_PANIC_HANG is enabled.
+ *
+ * This function does not return.
+ */
+void hang(void) __attribute__ ((noreturn));
+#endif
+
+#endif