[media] coda: improve safety in coda_register_device()

The "i" variable is used as an offset into both the dev->vfd[] and the
dev->devtype->vdevs[] arrays.  The second array is smaller so we should
use that as a limit instead of ARRAY_SIZE(dev->vfd).  Also the original
check was off by one.

We should use a format string as well in case the ->name has any funny
characters and also to stop static checkers from complaining.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>