drm/i915: Fix misplaced '\n' in printing the GPU error's RING_HEAD

'\n' is supposed to be at the end of the line, not in the middle.

Fixes: cdb324bd ("drm/i915: Show bounds of active request in the ring...")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161013101815.26978-2-chris@chris-wilson.co.uk