mm/vmscan: change comment generic_file_write to __generic_file_aio_write

Commit 543ade1fc9 ("Streamline generic_file_* interfaces and filemap
cleanups") removed generic_file_write() in filemap.  Change the comment in
vmscan pageout() to __generic_file_aio_write().

Signed-off-by: Vincent Li <macli@brc.ubc.ca>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -358,7 +358,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
 	 * stalls if we need to run get_block().  We could test
 	 * PagePrivate for that.
 	 *
-	 * If this process is currently in generic_file_write() against
+	 * If this process is currently in __generic_file_aio_write() against
 	 * this page's queue, we can perform writeback even if that
 	 * will block.
 	 *