drm/i915: Make global seqno known in i915_gem_request_execute tracepoint

Commit fe49789f

 ("drm/i915: Deconstruct execute fence") re-arranged
the code and moved the i915_gem_request_execute tracepoint to before the
global seqno is assigned to the request.

We need to move the tracepoint a bit later so this information is once
again available.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: fe49789f

 ("drm/i915: Deconstruct execute fence")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180220104742.565-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit 158863fb

)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>