Add an implementation of get_next_write_timestamp.

Add a default implementation of get_next_write_timestamp to the C <--> C++
legacy audio HAL implementation allowing HALs using the legacy C++
AudioStreamOut to overload and implement get_next_write_timestamp.  Default
implementation returns INVALID_OPERATION to indicate that the functionality is
not supported.

Change-Id: I087347649e9ba186a74cb34aaadf989bf90720fe
3 files changed