drm/amdgpu: cancel gfx idle work in device suspend for s0ix

This is normally handled in the gfx IP suspend callbacks, but
for S0ix, those are skipped because we don't want to touch
gfx.  So handle it in device suspend.

Fixes: b9467983 ("drm/amdgpu: add dynamic workload profile switching for gfx10")
Fixes: 963537ca ("drm/amdgpu: add dynamic workload profile switching for gfx11")
Fixes: 5f95a154 ("drm/amdgpu: add dynamic workload profile switching for gfx12")
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>