msm: ADSPRPC: Free file private data after session close

Release the session before the file data is freed to
allow for session informaiton to be retrieved from the
file data.

Change-Id: I78c36d7b34a141c6162a145f7447040395858b64
Acked-by: Bharath Kumar <bkumar@qti.qualcomm.com>
Signed-off-by: Sathish Ambley <sathishambley@codeaurora.org>