PEL: Const flatten for BCDTime

It doesn't modify the object, so can be const.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Ib3bbe2b8467578b0cddce0284aa6ae95f1ad826a
diff --git a/extensions/openpower-pels/bcd_time.hpp b/extensions/openpower-pels/bcd_time.hpp
index 86d9f4e..72c5755 100644
--- a/extensions/openpower-pels/bcd_time.hpp
+++ b/extensions/openpower-pels/bcd_time.hpp
@@ -90,7 +90,7 @@
  *
  * @return Stream&
  */
-Stream& operator<<(Stream& s, BCDTime& time);
+Stream& operator<<(Stream& s, const BCDTime& time);
 
 } // namespace pels
 } // namespace openpower