V4L/DVB (12770): Add tm6000 driver to staging tree

Adds a driver for Trident TV Master tm5600/tm6000 chips.

Those USB devices are usually found with a Xceive xc2028/xc3028
tuner, although the firmware seems to be modified to work with
those chips on some older devices.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>