V4L/DVB (10127): stv06xx: Avoid having y unitialized

As pointed by gcc:

drivers/media/video/gspca/stv06xx/stv06xx_hdcs.c: In function ‘hdcs_set_size’:
drivers/media/video/gspca/stv06xx/stv06xx_hdcs.c:301: warning: ‘y’ may be used uninitialized in this function

Signed-off-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>