ASoC: msm: qdsp6v2: Correctly free ASM no wait queue

Remove improper deletion of list head and protect list
deletion with spinlock. Spinlock protects the list
from access in ADSP callback at the same time the
list is being deallocated.

Change-Id: I1b102cd99e7c80e1dfd4e2054b9ba7e0ca26d6a7
Signed-off-by: Ben Romberger <bromberg@codeaurora.org>