bis_factory: Add accessor for NAND Image Directory

src/core/file_sys/bis_factory.cpp

@@ -88,4 +88,8 @@ VirtualFile BISFactory::OpenPartitionStorage(BisPartitionId id) const {
     }
 }
 
+VirtualDir BISFactory::GetImageDirectory() const {
+    return GetOrCreateDirectoryRelative(nand_root, "/user/Album");
+}
+
 } // namespace FileSys

src/core/file_sys/bis_factory.h

@@ -49,6 +49,8 @@ public:
     VirtualDir OpenPartition(BisPartitionId id) const;
     VirtualFile OpenPartitionStorage(BisPartitionId id) const;
 
+    VirtualDir GetImageDirectory() const;
+
 private:
     VirtualDir nand_root;
     VirtualDir load_root;