V4L/DVB: gspca - zc3xx: Cleanup source

- use an enum to define the sensor numbers
- use the sensor numbers to index the associated tables
- rename TAS5130CXX to TAS5130C
- rename HV7131C to HV7131R
- change some comments

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