drm/amdgpu: Remove amdgpu_device arg from free_sgt api (v2)

Currently callers have to provide handle of amdgpu_device,
which is not used by the implementation. It is unlikely this
parameter will become useful in future, thus removing it

v2: squash in unused variable fix

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>