drm/amdgpu: explicit give BO type to amdgpu_bo_create

Drop the "kernel" and sg parameter and give the BO type to create
explicit to amdgpu_bo_create instead of figuring it out from the
parameters.

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