Add a namespace to OpenFStream

For consistency with the other functions in FileUtil.h.

Source/Core/Core/PowerPC/SignatureDB/CSVSignatureDB.cpp

@@ -18,7 +18,7 @@ bool CSVSignatureDB::Load(const std::string& file_path)
 {
   std::string line;
   std::ifstream ifs;
-  OpenFStream(ifs, file_path, std::ios_base::in);
+  File::OpenFStream(ifs, file_path, std::ios_base::in);
 
   if (!ifs)
     return false;

Source/Core/Core/PowerPC/SignatureDB/MEGASignatureDB.cpp

@@ -128,7 +128,7 @@ void MEGASignatureDB::Clear()
 bool MEGASignatureDB::Load(const std::string& file_path)
 {
   std::ifstream ifs;
-  OpenFStream(ifs, file_path, std::ios_base::in);
+  File::OpenFStream(ifs, file_path, std::ios_base::in);
 
   if (!ifs)
     return false;