V4L/DVB (13561): gspca - main: Remove unnecessary set to alternate 0.

Calling gspca_set_alt0() in gspca_dev_probe() is not needed as gspca_set_alt0()
will do nothing because gspca_dev->alt is always zero at that time.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>