V4L/DVB: tm6000: add special usb request to quit i2c tuner transfer

After sending an i2c command, tm6010 needs a reset, in order to properly
work.

While here, add the missing I2C_CLASS_TV_DIGITAL i2c class.

Signed-off-by: Stefan Ringel <stefan.ringel@arcor.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>