drm/nouveau/pmu/gm200-: avoid touching PMU outside of DEVINIT/PREOS/ACR

[ Upstream commit 1d2271d2fb85e54bfc9630a6c30ac0feb9ffb983 ]

There have been reports of the WFI timing out on some boards, and a
patch was proposed to just remove it.  This stuff is rather fragile,
and I believe the WFI might be needed with our FW prior to GM200.

However, we probably should not be touching PMU during init on GPUs
where we depend on NVIDIA FW, outside of limited circumstances, so
this should be a somewhat safer change that achieves the desired
result.

Reported-by: Diego Viola <diego.viola@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://gitlab.freedesktop.org/drm/nouveau/-/merge_requests/10


Signed-off-by: Sasha Levin <sashal@kernel.org>