Add missing files to Debian DKMS package

Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Umer Saleem <usaleem@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Damiano Albani <damiano.albani@gmail.com>
Closes #14887
Closes #14889