omapdrm: hdmi4: hook up the HDMI CEC support

Hook up the HDMI CEC support in the hdmi4 driver.

It add the CEC irq handler, the CEC (un)init calls and tells the CEC
implementation when the physical address changes.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>