block: unexport bdev_read_page and bdev_write_page

Each one just has two callers, both in always built-in code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -714,7 +714,6 @@ int bdev_read_page(struct block_device *bdev, sector_t sector,
 	blk_queue_exit(bdev->bd_queue);
 	return result;
 }
-EXPORT_SYMBOL_GPL(bdev_read_page);
 
 /**
  * bdev_write_page() - Start writing a page to a block device
@@ -759,7 +758,6 @@ int bdev_write_page(struct block_device *bdev, sector_t sector,
 	blk_queue_exit(bdev->bd_queue);
 	return result;
 }
-EXPORT_SYMBOL_GPL(bdev_write_page);
 
 /*
  * pseudo-fs