Copy AudioPort.h to libaudiofoundation.

Copy AudioPort.h from audio policy to libaudiofoundation and name it as
AudioPortBase.h. Note that AudioPortBase has not been added into the
make file as it needs some more change to make it work. Doing this just
to make a cleaner diff for later change.

Bug: 135621476
Test: make
Change-Id: I6cd1a53e889340c7fefffdd5832854016cd733ee
Merged-In: I6cd1a53e889340c7fefffdd5832854016cd733ee