hw/net/can: sja1000 fix buff2frame_bas and buff2frame_pel when dlc is out of std...

hw/net/can: sja1000 fix buff2frame_bas and buff2frame_pel when dlc is out of std CAN 8 bytes

Problem reported by openEuler fuzz-sig group.

The buff2frame_bas function (hw\net\can\can_sja1000.c)
infoleak(qemu5.x~qemu6.x) or stack-overflow(qemu 4.x).

Reported-by: Qiang Ning <ningqiang1@huawei.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Jason Wang <jasowang@redhat.com>