Remove tx_status event in CEC HAL

Removes tx_status event type which turns out not in actual use.
This changes makes send_message() work in sychrnonous fashion
when called by HdmiControlService. HdmiControlService has io thread
dedicated to interact with HAL, hence no need to introduce
another async flow for HAL.

Change-Id: I8ae21b1149cd36bfd0f9da215c4f23b30f0c8d30
1 file changed