drm/i915: Redo "Remove i915_request.lock requirement for execution callbacks"

The reordering and rebasing of commit 2e4c6c1a9db5 ("drm/i915: Remove
i915_request.lock requirement for execution callbacks") caused it to
revert an earlier correction. Let us restore commit 99f0a640d464
("drm/i915: Remove requirement for holding i915_request.lock for
breadcrumbs")

Fixes: 2e4c6c1a9db5 ("drm/i915: Remove i915_request.lock requirement for execution callbacks")
Signed-off-by: Chris Wilson <[e-mail]>
Cc: Tvrtko Ursulin <[e-mail]>
Cc: Rodrigo Vivi <[e-mail]>
Cc: Joonas Lahtinen <[e-mail]>
Reviewed-by: Tvrtko Ursulin <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
(cherry picked from commit 35faeb7de9ef83da510a048f2016061f1e31d5fc)
Signed-off-by: Rodrigo Vivi <[e-mail]>

drivers/gpu/drm/i915/i915_request.c

···
 	__notify_execute_cb_irq(request);
 
 	/* We may be recursing from the signal callback of another i915 fence */
-	if (!i915_request_signaled(request)) {
-		spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING);
-
-		if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
-			     &request->fence.flags) &&
-		    !i915_request_enable_breadcrumb(request))
-			intel_engine_signal_breadcrumbs(engine);
-
-		spin_unlock(&request->lock);
-	}
+	if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags))
+		i915_request_enable_breadcrumb(request);
 
 	return result;
 }