MultiAccessUnits: offset size fixes for secure API

Encrypted buffer offsets were updated with the correct
values.

Bug: 325512893

Test: atest android.mediav2.cts.CodecDecoderDrmTest
Test: atest android.mediav2.cts.CodecDecoderMultiAccessUnitDrmTest
Test: atest android.mediav2.cts.CodecDecoderBlockModelMultiAccessUnitDrmTest

Change-Id: I61283c6b28d67d48562568cd22d9a143d70668d0

WIP fix buffer sizes

Change-Id: Ife52478884e9bb65b6955199567fc1ff560e0fa2