f2fs: call f2fs_unlock_op after error was handled

This patch relocates f2fs_unlock_op in every directory operations to be called
after any error was processed.
Otherwise, the checkpoint can be entered with valid node ids without its
dentry when -ENOSPC is occurred.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --cc fs/f2fs/f2fs.h
Simple merge

diff --cc fs/f2fs/inode.c
Simple merge

diff --cc fs/f2fs/namei.c
Simple merge