fs/ntfs3: Fix error code in indx_add_allocate()

Return -EINVAL if ni_find_attr() fails.  Don't return success.

Fixes: 82cae269 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>