test: openpower-pels: Fix unscoped use of DoAll

This is in the global scope on old releases of googletest but is fixed
and inaccessible when tested against newer ones.

Change-Id: I139f2455bb804e1c711c5eec3159164d9ac138fa
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/openpower-pels/pel_test.cpp b/test/openpower-pels/pel_test.cpp
index 3fa3d55..984f2ec 100644
--- a/test/openpower-pels/pel_test.cpp
+++ b/test/openpower-pels/pel_test.cpp
@@ -27,6 +27,7 @@
 namespace fs = std::filesystem;
 using namespace openpower::pels;
 using ::testing::_;
+using ::testing::DoAll;
 using ::testing::NiceMock;
 using ::testing::Return;
 using ::testing::SetArgReferee;