drm/msm: show task cmdline in gpu recovery messages

Now that freedreno gallium driver defaults to using submit_queue task
(render reordering), just showing task->comm is not so useful (ie. it is
always "flush_queue:0"), so also dump the cmdline.  This should also be
more useful for piglit/shader_runner.

Signed-off-by: Rob Clark <robdclark@gmail.com>