media: adv7180: Only validate format in querystd

media: adv7180: Only validate format in querystd

The .querystd callback should not program the device with the detected
standard, it should only report the standard to user-space. User-space
may then use .s_std to set the standard, if it wants to use it.

All that is required of .querystd is to setup the auto detection of
standards and report its findings.

While at it add some documentation on why this can't happen while
streaming and improve the error handling using a scoped guard.

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