checkpatch: add a --strict check for utf-8 in commit logs

checkpatch: add a --strict check for utf-8 in commit logs

Some find using utf-8 in commit logs inappropriate.

Some patch commit logs contain unintended utf-8 characters when doing
things like copy/pasting compilation output.

Look for the start of any commit log by skipping initial lines that look
like email headers and "From: " lines.

Stop looking for utf-8 at the first signature line.

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Message-id: 20180430124651.10340-2-stefanha@redhat.com
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 15662b3e8644905032c2e26808401a487d4e90c1)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Conflicts:
  QEMU does not have CHK(), use WARN() instead.

  QEMU WARN() only takes one argument, drop the 'type' value in the
  first argument.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>