ASoc: msm: Serialize soc dsp trigger commands.

- Fast Device switching during playback is resulting in
backend dai shutdown is being invoked before startup is
processed.
- Fix the issue by protecting the trigger function with
spinlock to serialize trigger start and stop cmds.

CRs-fixed: 348790
Change-Id: Id18c4e535ed47c8307d59ad80073335a67a31e13
Signed-off-by: Jayasena Sangaraboina <jsanga@codeaurora.org>