generic: test negative SEEK_HOLE/SEEK_DATA offsets

Check that we get -ENXIO if the user calls SEEK_HOLE/SEEK_DATA with
a negative file offset.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
4 files changed