msm: npu: Fix SSR issue due to race condition

NPU SSR is handled in worker thread, so race condition can happen
between SSR thread and user app threads when SSR is triggered which
will cause unpredictable stability issue. This change is to add a
mutex to serialize npu fw init/deinit and ipc operations to resolve
this issue.

Change-Id: Ib6dcde76995193a5586a2164c12f56f8cf95518f
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>