HDMI: In offline mode, allow users to keep CEC enabled

Offline mode doesn't have energy modes and it defaults to low. This
means that we have to allow users to keep CEC enabled when the device
goes to sleep as an extension of the patch ag/29518409.

Test: atest com.android.server.hdmi
Bug: 380311953
Flag: EXEMPT urgent feature

Change-Id: I4a7e2a4cd6e8aac6771ce7449b979d3792578151