ASoC: msm: ensure check before accessing session private data.

The compressed session needs to be active to set volume to dsp.
Ensure the check to see valid session exist before accessing
private data, else results in kernel panic.

The Memory allocation for driver data also needs to be freed
for failure in session open.

CRs-Fixed: 638817
Change-Id: Ifdce543aa55df420960e9eeff0564f18d9410060
Signed-off-by: Asish Bhattacharya <asishb@codeaurora.org>