drm/i915: Immediately process a reset before starting waiting

As we handoff the GPU reset to the waiter, we need to check we don't
miss a wakeup if it has already been sent prior to us starting the wait.

v2: Tweak checking for reset to be clear to the need before sleeping
after changing the task state.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170223074422.4125-16-chris@chris-wilson.co.uk


Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>