doc: add author on cc to git fixline alias

doc: add author on cc to git fixline alias

With this commit, the correct method to use git fixline to indicate
a fix of a previous commit has changed. The new rules require the
author of the original code that is being fixed to be on CC.

The logic behind this improvement is that if there is a genuine bug,
one of the ideal people to review is the author of the original code
being fixed. Adding them on Cc makes them aware of the patch, avoiding
it from being passed by accidentally while reading the mailing-list.

Given that the original author (now on Cc:) might not actually review,
there is no value in keeping the Cc: in git commit history. If the
original author performs a review, their Reviewed-by: or Acked-by: is
stored in git history (same as now).

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>