checkpatch: add Co-authored-by to signature list

Co-authored-by is commonly used for changes that have more than one
author. Add it to the list to make Jenkins happy.

Change-Id: I7f66824febe3be756c64ebf44c94bc653a66f1e1
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69166
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Patrick Georgi <patrick@coreboot.org>

0 files changed, 0 insertions, 0 deletions