[media] sur40: drop unnecessary format description

Don't fill in the format description. This is now done in the V4L2 core to ensure
consistent descriptions.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Nick Dyer <nick.dyer@itdev.co.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>