drm/i915: Add is-wedged flag to intel_engine_dump()

Comparing the state tested by intel_engine_is_idle() and printed by
intel_engine_dump(), the only bit not shown is whether or not the device
is wedged. Add that little bit of information to the pretty printer so
that if the engine fails to idle we can see why.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171208012303.25504-5-chris@chris-wilson.co.uk