drm/i915/gt: Expand bad CS completion event debug

Show the ring/request/context state if we see what we believe is an
early CS completion.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211230944.1203098-1-chris@chris-wilson.co.uk