drm/radeon: Add radeon_test_syncing function v2

Tests syncing between all rings by using
semaphores and fences.

v2: use radeon_testing as a bit flag rather than on/off switch
    this allow to test for one thing at a time (bo_move or semaphore
    test). It kind of break the usage if user wheren't using 1
    for bo move test but as it's a test feature i believe it's ok.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>