ASoC: msm: qdsp6v2: Do not free memory that has not been unmapped from DSP

The memory that is not unmapped from DSP should not be used until
DSP clears it. Do not free iom memory if the DSP unmap has
failed.

CRs-fixed: 599780
Change-Id: I4ceae34e0f8d6381efc34ce642babbc30ca5e57e
Signed-off-by: Damir Didjusto <damird@codeaurora.org>