nilfs2: delete mark_inode_dirty in nilfs_commit_chunk

Delete mark_inode_dirty() in nilfs_commit_chunk(), for callers of
nilfs_commit_chunk() will call equivalent mark_inode_dirty()
after calling nilfs_commit_chunk().

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