V4L/DVB (8231): gspca: Do not declare the webcams declared by other drivers.

etoms:    Do not declare the webcams declared by the driver et61x251.
sonixb, sonixj:
          Do not declare the webcams declared by the driver sn9c102.
zc3xx:    Do not declare the webcams declared by the driver zc0301.

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