drm/i915: Reorder submitting the requests to ELSP

Just rearrange the code to reduce churn in the next patch.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-5-chris@chris-wilson.co.uk