[MIPS] unwind_stack should return a value ...

And gcc 3.4 doesn't even warn out this, grrr.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/stacktrace.h b/include/asm-mips/stacktrace.h
index 87bd7ca..0bf8281 100644
--- a/include/asm-mips/stacktrace.h
+++ b/include/asm-mips/stacktrace.h
@@ -12,6 +12,7 @@
 static inline unsigned long unwind_stack(struct task_struct *task,
 	unsigned long *sp, unsigned long pc, unsigned long *ra)
 {
+	return 0;
 }
 #endif