drm/i915: Call io_schedule() whilst whilsting for the GPU

Since we are waiting upon IO completion, inform the kernel through use
of the io_schedule() call rather than the regular schedule(). This
should allow the kernel to make better decisions regarding scheduling
and power management.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 13c885d..7dc9c9c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1082,7 +1082,7 @@
 			mod_timer(&timer, expire);
 		}
 
-		schedule();
+		io_schedule();
 
 		if (timeout)
 			timeout_jiffies = expire - jiffies;