[media] vb2-core: call threadio->fnc() if !VB2_BUF_STATE_ERROR

changeset 70433a15 ("media: videobuf2: Refactor vb2_fileio_data
and vb2_thread") broke videobuf2-dvb.

The root cause is that, instead of calling threadio->fnc() for
all types of events except for VB2_BUF_STATE_ERROR, it was calling
it only for VB2_BUF_STATE_DONE.

With that, the DVB thread were never called.

Cc: stable@vger.kernel.org # Kernel >= 4.3
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>