camcontrol.8: Descriptions before examples

This page has a lot of examples, so having them in the previous order
can be confusing. Rewrite to the normal order where the descriptions
come before the command, followed by a colon, which is still clear even
jumping to the middle of the section.

PR: 291759
MFC after: 3 days
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D54285