V4L/DVB (10111): quickcam_messenger.c: fix a warning

drivers/media/video/usbvideo/quickcam_messenger.c: In function ‘qcm_sensor_init’:
drivers/media/video/usbvideo/quickcam_messenger.c:450: warning: operation on ‘ret’ may be undefined

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>