V4L/DVB: gspca - t613: Add color controls

- Rename controls to fit real behaviour
- Add global gain , r/b balance.

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