ASoC: msm: qdsp6v2: Index check for out of range

Check if index is a non-negative value before it is used.
Also, initialize return variable to default value before
it is used so that it does not return uninitialized value.

CRs-Fixed: 1059495
Change-Id: I94a6fc02436734b4f398d1a72f53b3ae68612679
Signed-off-by: Vikram Panduranga <vpandura@codeaurora.org>