media: pvrusb2: fix memory leak in pvr_probe

media: pvrusb2: fix memory leak in pvr_probe

The error handling code in pvr2_hdw_create forgets to unregister the
v4l2 device. When pvr2_hdw_create returns back to pvr2_context_create,
it calls pvr2_context_destroy to destroy context, but mp->hdw is NULL,
which leads to that pvr2_hdw_destroy directly returns.

Fix this by adding v4l2_device_unregister to decrease the refcount of
usb interface.

Reported-by: syzbot+77b432d57c4791183ed4@syzkaller.appspotmail.com
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>