msm: vidc: set EOS on output buffer pending transaction

If EOS is signalled while an output buffer is in transaction,
mark EOS when that buffer is returned.
This is observed in case client sends an empty buffer with EOS

Change-Id: I9b4ce6331eb7a70886c1802d1f99e1d77d65fa64
Signed-off-by: Deepak Verma <dverma@codeaurora.org>