nro: Make LoadNro take a VfsFile by const reference

This function doesn't need to care about ownership semantics, so we can
just pass it a reference to the file itself, rather than a
std::shared_ptr alias.

src/core/loader/nro.h

@@ -41,7 +41,7 @@ public:
     bool IsRomFSUpdatable() const override;
 
 private:
-    bool LoadNro(FileSys::VirtualFile file, VAddr load_base);
+    bool LoadNro(const FileSys::VfsFile& file, VAddr load_base);
 
     std::vector<u8> icon_data;
     std::unique_ptr<FileSys::NACP> nacp;