drm/amdgpu: enable swiotlb for gmc 10.0 (V2)

Enable swiotlb for gmc 10.0.
v2: include drm_cache.h to use the function ‘drm_need_swiotlb’

Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>