[S390] bug: implement arch specific __WARN macro

This one will trap, generates shorter code and emits better debug data
than the generic version.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/bug.h

@@ -52,6 +52,10 @@
 	unreachable();					\
 } while (0)
 
+#define __WARN() do {					\
+	__EMIT_BUG(BUGFLAG_WARNING);			\
+} while (0)
+
 #define WARN_ON(x) ({					\
 	int __ret_warn_on = !!(x);			\
 	if (__builtin_constant_p(__ret_warn_on)) {	\