CODING_STYLE: Define our preferred form for multiline comments

CODING_STYLE: Define our preferred form for multiline comments

The codebase has a bit of a mix of different multiline
comment styles. State a preference for the Linux kernel
style:
    /*
     * Star on the left for each line.
     * Leading slash-star and trailing star-slash
     * each go on a line of their own.
     */

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180611141716.3813-1-peter.maydell@linaro.org