media: tm6000: Fix memleak in tm6000_start_stream

When usb_clear_halt() fails, dvb->bulk_urb->transfer_buffer
and dvb->bulk_urb should be freed just like when
usb_submit_urb() fails.

Fixes: 3169c9b2

 ("V4L/DVB (12788): tm6000: Add initial DVB-T support")
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>