media: s3c-camif: add missing description at s3c_camif_find_format()

Fix this warning:
	drivers/media/platform/s3c-camif/camif-core.c:112: warning: No description found for parameter 'vp'
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/s3c-camif/camif-core.c

@@ -103,6 +103,7 @@ static const struct camif_fmt camif_formats[] = {
 
 /**
  * s3c_camif_find_format() - lookup camif color format by fourcc or an index
+ * @vp: video path (DMA) description (codec/preview)
  * @pixelformat: fourcc to match, ignored if null
  * @index: index to the camif_formats array, ignored if negative
  */