drm/i915/selftests: Include engine name after reset failure

During igt_reset_nop_engine, an engine reset unexpectedly failed. For the
next time this happens, mention which engine that was.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111105735.21515-4-chris@chris-wilson.co.uk