softFlac: handle eos buffers at any stage

Test: make vts -j99 BUILD_GOOGLE_VTS=true TARGET_PRODUCT=aosp_arm64 \
&& vts-tradefed run commandAndExit vts \
--skip-all-system-status-check --primary-abi-only \
--skip-preconditions --module VtsHalMediaOmxV1_0Host \
-l INFO

Bug: 63796949

Change-Id: I528b4bc041aab8affc28cb7d1b96ea6065754798
1 file changed