Vanshidhar Konda asked for the simplest test "to verify that the kernel
can submit and hardware can execute batch buffers on all the command
streamers in parallel." We have a number of tests in userspace that
submit load to each engine and verify that it is present, but strictly
we have no selftest to prove that the kernel can _simultaneously_
execute on all known engines. (We have tests to demonstrate that we can
submit to HW in parallel, but we don't insist that they execute in
parallel.)

v2: Improve the igt_spinner support for older gen.
Suggested-by: Vanshidhar Konda <vanshidhar.r.konda@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Vanshidhar Konda <vanshidhar.r.konda@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Vanshidhar Konda <vanshidhar.r.konda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191101101528.10553-1-chris@chris-wilson.co.uk