Try to fix FreeBSD build after IWYU changes.

llvm-svn: 299719
diff --git a/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp b/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp
index abdbb8b..b336531 100644
--- a/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp
+++ b/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp
@@ -24,6 +24,7 @@
 
 // Other libraries and framework includes
 #include "lldb/Core/PluginManager.h"
+#include "lldb/Core/RegisterValue.h"
 #include "lldb/Core/State.h"
 #include "lldb/Host/Host.h"
 #include "lldb/Symbol/ObjectFile.h"