ASoC: msm: Null dereference check added

In asm_read function we should check buffer pointer
before it is dererferenced.

CRs-Fixed: 612682
Change-Id: I1968c038e1d35381bf174000287d542441e41092
Signed-off-by: Anish Kumar <kanish@codeaurora.org>
Merge "ASoC: msm: Null dereference check added" into du44