media: adv7180: Disable test-pattern control on adv7180

The register that enables selecting a test-pattern to be outputted in
free-run mode (FREE_RUN_PAT_SEL[2:0]) is only available on adv7280 based
devices, not the adv7180 based ones.

Add a flag to mark devices that are capable of generating test-patterns,
and those that are not. And only register the control on supported
devices.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>