libstagefright: Copy the entire buffer from/to OMX component

Presence of OMX extradata in buffers isn't reflected as part of
nFilledLen.  To avoid omitting the extradata, copy the entire buffer.

Change-Id: Ib310dda3dc93693d4ab380912a9997d7ea120be1
Merge "libstagefright: Copy the entire buffer from/to OMX component" into du44