Ext2FS: Deallocate block list meta blocks when freeing an inode

When computing the list of blocks to deallocate when freeing an inode,
we would stop collecting blocks after reaching the inode's block count.
Since we're getting rid of the inode, we need to also include the meta
blocks used by the on-disk block list itself.

Kernel/FileSystem/Ext2FileSystem.h

@@ -165,7 +165,7 @@ private:
         unsigned meta_blocks { 0 };
     };
 
-    BlockListShape compute_block_list_shape(unsigned blocks);
+    BlockListShape compute_block_list_shape(unsigned blocks) const;
 
     unsigned m_block_group_count { 0 };