[media] au0828: move dev->boards atribuition to happen earlier

The attribution of dev->boards occured too late, which
would couse an OOPS in media controller registration.

Signed-off-by: Rafael Lourenço de Lima Chehab <chehabrafael@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>