fs/ntfs3: Slightly simplify ntfs_inode_printk()

The size passed to snprintf() includes the space for the trailing space.
So there is no reason here not to use all the available space.

So remove the -1 when computing 'name_len'.
While at it, use the size of the array directly instead of the intermediate
'name_len' variable.

snprintf() also guaranties that the buffer if NULL terminated, so there is
no need to write an additional trailing NULL "To be sure".

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>