FileSystem: Don't expose VFS::root_inode().

It seems like we don't need to expose this anymore, it's only used by VFS
internally to construct the root custody.

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -617,7 +617,7 @@ void VFS::sync()
 Custody& VFS::root_custody()
 {
     if (!m_root_custody)
-        m_root_custody = Custody::create(nullptr, "", *root_inode());
+        m_root_custody = Custody::create(nullptr, "", *m_root_inode);
     return *m_root_custody;
 }
 

Kernel/FileSystem/VirtualFileSystem.h

@@ -90,8 +90,6 @@ public:
     void for_each_mount(Function<void(const Mount&)>) const;
 
     InodeIdentifier root_inode_id() const;
-    Inode* root_inode() { return m_root_inode.ptr(); }
-    const Inode* root_inode() const { return m_root_inode.ptr(); }
 
     void sync();