V4L/DVB (8154): Fix protection problems in the main driver.

- Protect format change when streaming active.
- Protect USB exchanges on close.
- Set a timeout in frame wait.
- Have only one capture file and free the resources when closing this file.
- Simplify the URB buffer.
- Don't reset the control values at open time in pac207.
- Fix compilation warnings of stk014.

Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>