tests/gem_barrier_race: Extend support over compute engines

This test can work not only on render engines, as its current code
suggests, but also on compute class engines.  Add them to the set of
engine classes supported by the test, in case a future platform has only
those and no RCS available.

Suggested-by: Chris Wilson <chris.p.wilson@linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>