arm: walk_stacktrace() needs to be exported

oprofile depends on having it
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/kernel/stacktrace.c

+#include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/stacktrace.h>
 
@@ -30,6 +31,7 @@ int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
 
 	return 0;
 }
+EXPORT_SYMBOL(walk_stackframe);
 
 #ifdef CONFIG_STACKTRACE
 struct stack_trace_data {