drm/i915: Use an uninterruptible wait for page-flips during modeset

We need to drain the pending flips prior to disabling the pipe during
modeset, and these need to be done in an uninterruptible fashion.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 174e38a..dec7bbc 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3506,7 +3506,7 @@
 	return 0;
 }
 
-int
+static int
 i915_gem_wait_for_pending_flip(struct drm_device *dev,
 			       struct drm_gem_object **object_list,
 			       int count)