fs/ntfs3: remove atomic_open

atomic_open is an optional VFS operation, and is primarily for network
filesystems. NFS (for instance) can just send an open call for the last
path component rather than doing a lookup and then having to follow that
up with an open when it doesn't have a dentry in cache.

ntfs3 is a local filesystem however, and its atomic_open just does a
typical lookup + open, but in a convoluted way. atomic_open will also
make directory leases more difficult to implement on the filesystem.

Remove ntfs_atomic_open.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>