Relax the wording about line lengths a little bit; this goes with the
checkpatch changes to warn at 100 characters rather than 80.

(Compare the Linux kernel commit bdc48fa11e46f8; our coding style is
not theirs, but the rationale is good and applies to us too.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20201106112940.31300-1-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>