[media] au0828: fix a couple of missed edge cases for i2c gate with analog

This patch addresses a couple of cases where I forgot to pop open the
gate when in analog mode (a correlary to fix the change made in patch
1c58d5b4a5fca42dce5428bd79b9405878017735).

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>