[media] go7007-usb: only use go->dev after allocated

Fixes those warnings:
	drivers/staging/media/go7007/go7007-usb.c: In function 'go7007_usb_probe':
	drivers/staging/media/go7007/go7007-usb.c:1060: warning: 'go' is used uninitialized in this function

While here, comment a code that will never run.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>