Fix infinite recursion

This commit fixes an idefinite recursion in
utility::readBusProperty by using a fully qualified
name for openpower::vpd::readBusProperty.

Tested:
Make sure calls to VPD manager work.

Signed-off-by: Santosh Puranik <santosh.puranik@in.ibm.com>
Change-Id: I70b0c29333a38705ccaaa54134d80b6c14e61832
diff --git a/utilInterface.hpp b/utilInterface.hpp
index 4f6009b..086f510 100644
--- a/utilInterface.hpp
+++ b/utilInterface.hpp
@@ -34,7 +34,7 @@
     std::string readBusProperty(const std::string& obj, const std::string& inf,
                                 const std::string& prop) override
     {
-        return readBusProperty(obj, inf, prop);
+        return openpower::vpd::readBusProperty(obj, inf, prop);
     }
 };