media: hdpvr: Fix an error handling path in hdpvr_probe()

Here, hdpvr_register_videodev() is responsible for setup and
register a video device. Also defining and initializing a worker.
hdpvr_register_videodev() is calling by hdpvr_probe at last.
So no need to flush any work here.
Unregister v4l2, free buffers and memory. If hdpvr_probe() will fail.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
