drm/i915: Look for active requests earlier in the reset path

drm/i915: Look for active requests earlier in the reset path

And store the active request so that we only search for it once.

v2: Check for request completion inside _prepare_engine, don't use
ECANCELED, remove unnecessary null checks (Chris).

v3: Capture active requests during reset_prepare and store it the
engine hangcheck obj.

v4: Rename commit, change i915_gem_reset_request to just confirm the
active_request is still incomplete, instead of engine_stalled (Chris).

v5: With style; pass the active request to gem_reset_engine, keep single
return in reset_prepare_engine (Chris).

v6: Moved before reset-engine code appears (Chris)

Suggested-by: Chris Wilson <[email protected]>
Reviewed-by: Chris Wilson <[email protected]> (v5)
Signed-off-by: Michel Thierry <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
Reviewed-by: Chris Wilson <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]