ntfs: drop nlink once for WIN32/DOS aliases

ntfs: drop nlink once for WIN32/DOS aliases

NTFS could store a filename as paired WIN32 and DOS $FILE_NAME attributes
for directories. But ntfs_delete() deleted both attributes for unlinking
a directory, but it also called drop_nlink() for each attributes.
This could trigger warnings when unlinking directories.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>