[media] drivers: video: cx231xx: Fix dependency for VIDEO_CX231XX_DVB

Fix the following build warning:

warning: (VIDEO_CX231XX_DVB) selects DVB_MB86A20S which has unmet direct dependencies (MEDIA_SUPPORT && DVB_CAPTURE_DRIVERS && DVB_CORE && I2C)

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>