media: adv7180: Only validate format in s_std

media: adv7180: Only validate format in s_std

The .s_std callback should not write the new format directly do the
device, it should only store it and have it applied by .s_stream.

As .s_stream already calls adv7180_program_std() all that is needed
is to check the standard is valid, and store it for .s_stream to
program.

While at it add a scoped guard to simplify the error handling.

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