[media] drivers/media/pci/zoran: avoid fragile snprintf use

Appending to a string by doing snprintf(buf, bufsize, "%s...", buf,
...) is not guaranteed to work.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>