[media] au8522: fix clamp control for different video modes

Straighten out the clamp control configurations for the various video modes,
based off of register diffs done against the Hauppauge Windows driver.

This work was sponsored by GetWellNetwork Inc.

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