media: platform: Add Amlogic Meson AO CEC Controller driver

The Amlogic SoC embeds a standalone CEC controller, this patch adds a driver
for such controller.
The controller does not need HPD to be active, and could support up to max
5 logical addresses, but only 1 is handled since the Suspend firmware can
make use of this unique logical address to wake up the device.

The Suspend firmware configuration will be added in an other patchset.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
[hans.verkuil@cisco.com:s/if (ret)/if (res)/ to fix obvious typo]
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>