drm/amdgpu: remove unnecessary save/restore of pdev->d3_delay

Remove unnecessary save/restore of pdev->d3_delay.

The only assignments to pdev->d3_delay are in radeon_switcheroo_set_state()
and some quirks, none of which should be relevant in the
amdgpu_switcheroo_set_state() path.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andreas Boll <andreas.boll.dev@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>