vfs: Replace mode.h include with forward declarations where applicable

Avoids the need to rebuild these source files if the mode header
changes.

src/core/file_sys/vfs.cpp

@@ -8,6 +8,7 @@
 #include "common/common_paths.h"
 #include "common/file_util.h"
 #include "common/logging/backend.h"
+#include "core/file_sys/mode.h"
 #include "core/file_sys/vfs.h"
 
 namespace FileSys {

src/core/file_sys/vfs.h

@@ -9,9 +9,8 @@
 #include <string_view>
 #include <type_traits>
 #include <vector>
-#include "boost/optional.hpp"
+#include <boost/optional.hpp>
 #include "common/common_types.h"
-#include "core/file_sys/mode.h"
 
 namespace FileSys {
 
@@ -19,6 +18,8 @@ class VfsDirectory;
 class VfsFile;
 class VfsFilesystem;
 
+enum class Mode : u32;
+
 // Convenience typedefs to use Vfs* interfaces
 using VirtualFilesystem = std::shared_ptr<VfsFilesystem>;
 using VirtualDir = std::shared_ptr<VfsDirectory>;