drm/i915: Remove request->reset_counter

drm/i915: Remove request->reset_counter

Since commit 2ed53a94d8cb ("drm/i915: On GPU reset, set the HWS
breadcrumb to the last seqno") once a hang is completed, the seqno is
advanced past all current requests. With this we know that if we wake up
from waiting for a request, if a hang has occurred and reset completed,
our request will be considered complete (i.e.
i915_gem_request_completed() returns true). Therefore we only need to
worry about the situation where a hang has occurred, but not yet reset,
where we may need to release our struct_mutex. Since we don't need to
detect the completed reset using the global gpu_error->reset_counter
anymore, we do not need to track the reset_counter epoch inside the
request.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467211874-11552-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Arun Siluvery <arun.siluvery@linux.intel.com>