Use : hex format for HdmiCecMessage.toString

ag/5340977

This format is used by both cec-client and www.cec-o-matic.com

Bug:117991662
Test: m -j; flashall; adb shell dumpsys hdmi_control
Change-Id: Icaf172a54eb776ca848d16f5e8384f17ae236207
1 file changed