[media] tw68: add original tw68 code

This tw68 driver has been out-of-tree for many years on gitorious:
https://gitorious.org/tw68/tw68-v2.

This copies that code to the kernel as a record of that original code.

Note that William Brack's email address in these sources is no longer
valid and I have not been able to contact him. However, all the code is
standard GPL.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>