[media] s5p-cec: add cec-notifier support, move out of staging

By using the CEC notifier framework there is no longer any reason
to manually set the physical address. This was the one blocking
issue that prevented this driver from going out of staging, so do
this move as well.

Update the bindings documenting the new hdmi phandle and
update exynos4.dtsi accordingly.

Tested with my Odroid U3.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
CC: linux-samsung-soc@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>