npcx: CEC: Send CEC message in mkbp event

Instead of fetching incoming CEC messages using a specific read
command, extend the standard mkbp event so the CEC message can
be delivered directly inside the event.

Signed-off-by: Stefan Adolfsson <sadolfsson@chromium.org>

BUG=b:76467407
BRANCH=none
TEST="ectool cec read" still working with a kernel that has support
for the increased mkbp size.
CQ-DEPEND=CL:1046186,CL:1051085

Change-Id: Id9d944be86ba85084b979d1df9057f7f3e7a1fd0
Reviewed-on: https://chromium-review.googlesource.com/1051105
Commit-Ready: Stefan Adolfsson <sadolfsson@chromium.org>
Tested-by: Stefan Adolfsson <sadolfsson@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
4 files changed