msm: npu: Fix SSR race condition issue in DSP mode

Once SSR occurs in DSP mode, npu_unmap has to be done after fw
is turned off completely. Otherwise iommu violation fault may
happen if the buffer is still used by the npu cal hw.

Change-Id: I56b4d8eac8a0f6901c8616a72c59e1d47343aeb4
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>