Kernel: Add FIBMAP ioctl to Ext2FileSystem

FIBMAP is a linux ioctl that gives the location on disk of a specific
block of a file

Kernel/FileSystem/Ext2FileSystem.h

@@ -77,6 +77,8 @@ private:
     virtual KResult chown(uid_t, gid_t) override;
     virtual KResult truncate(u64) override;
 
+    virtual KResultOr<int> get_block_address(int) override;
+
     bool write_directory(const Vector<Ext2FSDirectoryEntry>&);
     bool populate_lookup_cache() const;
     KResult resize(u64);