drm/i915: Fix unintended recursion in ironlake_disable_rc6

After disabling, we're meant to teardown the bo used for the contexts,
not recurse into ourselves again and preventing module unload.
Reported-and-tested-by: NBen Widawsky <bwidawsk@gmail.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -6575,7 +6575,7 @@ static void ironlake_disable_rc6(struct drm_device *dev)
 		POSTING_READ(RSTDBYCTL);
 	}
 
-	ironlake_disable_rc6(dev);
+	ironlake_teardown_rc6(dev);
 }
 
 static int ironlake_setup_rc6(struct drm_device *dev)