media: platform: meson: Add Amlogic Meson G12A AO CEC Controller driver

The Amlogic G12A SoC embeds a second CEC controller with a totally
different design.

The two controller can work in the same time since the CEC line can
be set to two different pins on the two controllers.

This second CEC controller is documented as "AO-CEC-B", thus the
registers will be named "CECB_" to differentiate with the other
AO-CEC driver.

Unlike the other AO-CEC controller, this one takes the Oscillator
clock as input and embeds a dual-divider to provide a precise
32768Hz clock for communication. This is handled by registering
a clock in the driver.

Unlike the other AO-CEC controller, this controller supports setting
up to 15 logical addresses and supports the signal_free_time settings
in the transmit function.

Unfortunately, this controller does not support "monitor" mode.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>