V4L/DVB (6225): AverTV Studio 307 has only one composite input

AverTV Studio 307 has only one composite input.

Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Acked-by: Nickolay V. Shmyrev <nshmyrev@yandex.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>