HDMI: improve buffer active source logic

Previous update did not account for all possible branches and might lead
to index out of bound error.

Bug: b/423940203
Test: atest HdmiCecLocalDeviceTvTest
Flag: EXEMPT bugfix only
Change-Id: I9bc08d0a2018120ff39db33d7f2a8a22c1745c80
1 file changed