V4L/DVB (3145): syncronizes some changes between v4l and dvb

- digitv_ctrl_msg() if (wo) test is reversed. fixed.
- usb timeout is in Hz, not in jiffies.
- NULL replaced by 0 to be coherent.
- removed uneeded headers.

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