[media] exynos_hdmi: add CEC notifier support

[media] exynos_hdmi: add CEC notifier support

Implement the CEC notifier support to allow CEC drivers to
be informed when there is a new physical address.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>