media: au0828 disable tuner to demod link in au0828_media_device_register()

Disable tuner to demod link in au0828_media_device_register(). This step
should be done after dvb graph is created.

[mchehab@osg.samsung.com: Solve conflictst to apply it upstream]
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>