haven: hh_msgq: Let clients manage the buffers for hh_msgq_send

Currently, the clients of the hh_msgq driver would allocate buffers,
fill with data and call hh_msgq_send(). Upon success, hh_msgq_send()
would be freeing the buffer, while in the case of failure, the clients
are responsible for it. However, this approach of buffer management is
not symmetric and could be confusing for the clients. Hence, let the
clients take full ownership of the buffers- allocating and freeing.

Also make changes to the affected client drivers.

Change-Id: I73101d823f9d3de16414e444fde494222f584e53
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>