V4L/DVB (9125): gspca: Big rewrite of t613 driver

- separate functions for bridge and sensor exchanges
- delays added after some exchanges
- other sensor type

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