media: cec: copy sequence field for the reply

When the reply for a non-blocking transmit arrives, the sequence
field for that reply was never filled in, so userspace would have no
way of associating the reply to the original transmit.

Copy the sequence field to ensure that this is now possible.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 0dbacebe ([media] cec: move the CEC framework out of staging and to media)
Cc: <stable@vger.kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>