asoc: msm: Fix zero size pointer issue

APPS crashes randomly due to invalid memory allocation
in q6asm_audio_client_buf_free_contiguous.
Added check to return error if memory allocation size is 0.

CRs-Fixed: 2308501
Change-Id: Ibc15fd6668a1abaeccdd400b42fdae8ff5093f9f
Signed-off-by: Soumya Managoli <smanag@codeaurora.org>