msm: npu: Power off npu until cpc power is off

Even after shutdown irq is received, NPUQ6 may not finish power
collapse yet. So it is necessary to wait until npu cpc is off
before turn off npu power.

Change-Id: I86a193354020f3c74c4260d4cbbfe16cd14aa7e3
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>