drm/i915: Use provided dma_fence_is_chain

Replace open-coded helper with the subsystem one.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20250512072047.56851-1-tvrtko.ursulin@igalia.com

Author: Tvrtko Ursulin

drivers/gpu/drm/i915/gem/i915_gem_wait.c

@@ -106,11 +106,6 @@ static void fence_set_priority(struct dma_fence *fence,
 	rcu_read_unlock();
 }
 
-static inline bool __dma_fence_is_chain(const struct dma_fence *fence)
-{
-	return fence->ops == &dma_fence_chain_ops;
-}
-
 void i915_gem_fence_wait_priority(struct dma_fence *fence,
 				  const struct i915_sched_attr *attr)
 {
@@ -126,7 +121,7 @@ void i915_gem_fence_wait_priority(struct dma_fence *fence,
 
 		for (i = 0; i < array->num_fences; i++)
 			fence_set_priority(array->fences[i], attr);
-	} else if (__dma_fence_is_chain(fence)) {
+	} else if (dma_fence_is_chain(fence)) {
 		struct dma_fence *iter;
 
 		/* The chain is ordered; if we boost the last, we boost all */