bdi: Drop 'parent' argument from bdi_register[_va]()

Drop 'parent' argument of bdi_register() and bdi_register_va().  It is
always NULL.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index aaeb2ec..557d840 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -25,11 +25,10 @@
 
 void bdi_put(struct backing_dev_info *bdi);
 
-__printf(3, 4)
-int bdi_register(struct backing_dev_info *bdi, struct device *parent,
-		const char *fmt, ...);
-int bdi_register_va(struct backing_dev_info *bdi, struct device *parent,
-		const char *fmt, va_list args);
+__printf(2, 3)
+int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...);
+int bdi_register_va(struct backing_dev_info *bdi, const char *fmt,
+		    va_list args);
 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
 void bdi_unregister(struct backing_dev_info *bdi);