msm: mdss: hdmi: add support for CEC suspend and resume events

Add support for CEC commands to suspend and resume the device.
The HDMI core must be kept on when the CEC wakeup feature is
enabled and the device is going into suspend state. Furthermore,
interrupts must be enabled in this state to capture CEC commands.
This allows the device to be resumed later on via CEC wakeup commands.

Change-Id: Ie6fcbc666e4f40335ab8faaa969d4b03aa83e17c
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>