This patch add cec driver for STM32 platforms.
cec hardware block isn't not always used with hdmi so
cec notifier is not implemented. That will be done later
when STM32 DSI driver will be available.

Driver compliance has been tested with cec-ctl and cec-compliance
tools.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: NYannick Fertre <yannick.fertre@st.com>
[hans.verkuil@cisco.com: modified platform/Makefile to use obj-y]
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>