msm: npu: handle system shutdown/reboot event properly

When system shuts down while there are work running on NPU,
NPUSS will be shut down without notifying kernel driver which
causes IPC commands timedout and triggers SSR handling.
This change is to detect this case and handle it properly
to avoid SSR.

Change-Id: I4ba6d702c2d39aa8e1894eba2ec049787df14aa8
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>