drm/amd: Stop evicting resources on APUs in suspend

commit 5095d541

 ("drm/amd: Evict resources during PM ops prepare()
callback") intentionally moved the eviction of resources to earlier in
the suspend process, but this introduced a subtle change that it occurs
before adev->in_s0ix or adev->in_s3 are set. This meant that APUs
actually started to evict resources at suspend time as well.

Explicitly set s0ix or s3 in the prepare() stage, and unset them if the
prepare() stage failed.

v2: squash in warning fix from Stephen Rothwell

Reported-by: Jürg Billeter <j@bitron.ch>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3132#note_2271038
Fixes: 5095d541

 ("drm/amd: Evict resources during PM ops prepare() callback")
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>