Move Android.mks to their parent dir.

So we don't need "../" to reference source files in the common/
directory.
"../" in LOCAL_SRC_FILES causes build race condition: the path of object
file of ../common/src/extra_data_handler.cpp in vdec actually is the
same
as the path of object file of ../common/src/extra_data_handler.cpp in
venc.

Bug: 12779537
Change-Id: I42bf0471451316dc61f5fafdde5bb1cf1f0218c3
(cherry picked from commit d919cadb)