fs: kill 'nr_pages' argument from wakeup_flusher_threads()

Everybody is passing in 0 now, let's get rid of the argument.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index d581579..1f9c6db 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -189,7 +189,7 @@ bool try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
 bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
 				   enum wb_reason reason);
 void sync_inodes_sb(struct super_block *);
-void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
+void wakeup_flusher_threads(enum wb_reason reason);
 void inode_wait_for_writeback(struct inode *inode);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */