drm/i915: Remove one level of indention from wait-for-execute

Now that the code is getting simpler, we can reduce the indentation when
waiting for the global_seqno.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170223074422.4125-17-chris@chris-wilson.co.uk