Adjust with changes in libxml2 upgrade

Bug: http://b/307806447
Test: TreeHugger
Change-Id: I474ca3539a2443ad0b1f590f27aa53a7279798e1
diff --git a/audio/common/all-versions/test/utility/src/ValidateXml.cpp b/audio/common/all-versions/test/utility/src/ValidateXml.cpp
index 4d6f003..b7e685b 100644
--- a/audio/common/all-versions/test/utility/src/ValidateXml.cpp
+++ b/audio/common/all-versions/test/utility/src/ValidateXml.cpp
@@ -19,6 +19,7 @@
 
 #include <numeric>
 
+#include <libxml/parser.h>
 #define LIBXML_SCHEMAS_ENABLED
 #include <libxml/xmlschemastypes.h>
 #define LIBXML_XINCLUDE_ENABLED