ilo: rework winsys batch buffer functions

ilo: rework winsys batch buffer functions

Rename

  intel_winsys_check_aperture_size() to intel_winsys_can_submit_bo(),
  intel_bo_exec() to intel_winsys_submit_bo(), and
  intel_winsys_decode_commands() to intel_winsys_decode_bo().

Make a semantic change to ignore intel_context when the ring is not the render
ring.