nilfs2: delete mark_inode_dirty in nilfs_delete_entry

Delete mark_inode_dirty() in nilfs_delete_entry() to reduce duplicate
mark_inode_dirty() calls both in nilfs_rename() and nilfs_delete_entry().

Signed-off-by: Jiro SEKIBA <jir@unicus.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>