In order to be more consistent with the rest of the request construction
and ring emission, use the common names for the ring and request.

Rather than using signaler_req, waiter_req, and intel_ring *wait, we use
plain req and ring.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-32-git-send-email-chris@chris-wilson.co.uk
Link: http://patchwork.freedesktop.org/patch/msgid/1470174640-18242-23-git-send-email-chris@chris-wilson.co.uk