drm/i915: Convert 'i915_seqno_passed' calls into 'i915_gem_request_completed'

Almost everywhere that caled i915_seqno_passed() was really asking 'has the
given seqno popped out of the hardware yet?'. Thus it had to query the current
hardware seqno and then do a signed delta comparison (which copes with wrapping
around zero but not with seqno values more than 2GB apart, although the latter
is unlikely!).

Now that the majority of seqno instances have been replaced with request
structures, it is possible to convert this test to be request based as well.
There is now a 'i915_gem_request_completed()' function which takes a request and
returns true or false as appropriate. Note that this currently just wraps up the
original _passed() test but a later patch in the series will reduce this to
simply returning a cached internal value, i.e.:
  _completed(req) { return req->completed; }'

This checkin converts almost all _seqno_passed() calls. The only one left is in
the semaphore code which still requires seqnos not request structures.

For: VIZ-4377
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Thomas Daniel <Thomas.Daniel@intel.com>
[danvet: Drop hunk touching the trace_irq code since I've dropped the
patch which converts that, and resolve resulting conflict.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>