[sysprof] util: add read_barrier() for ARMv7

[Christian Hergert <chergert src gnome org>]

commit 6ed7ec20ae17055f71e6180dc39aff468dda8932
Author: Christian Hergert <chergert redhat com>
Date:   Mon Aug 22 11:54:10 2016 -0700

    util: add read_barrier() for ARMv7

 lib/util/util.h |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/lib/util/util.h b/lib/util/util.h
index b0b55db..6062d43 100644
--- a/lib/util/util.h
+++ b/lib/util/util.h
@@ -29,4 +29,8 @@
 #define read_barrier()           asm volatile("" ::: "memory")
 #endif
 
+#ifdef __arm__
+#define read_barrier()           asm volatile("dsb" ::: "memory")
+#endif
+
 #endif /* SP_UTIL_H */