media: s5p_cec: limit msg.len to CEC_MAX_MSG_SIZE

media: s5p_cec: limit msg.len to CEC_MAX_MSG_SIZE

BugLink: https://bugs.launchpad.net/bugs/1998843
[ Upstream commit 93f65ce036863893c164ca410938e0968964b26c ]

I expect that the hardware will have limited this to 16, but just in
case it hasn't, check for this corner case.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>