[media] [trivial] davinci: Fix typo in dm355_ccdvc.c

Correct spelling "thresold" to "threshold" in
drivers/media/video/davinci/dm355_ccdc.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>