affs: use bdev_nr_sectors instead of open coding it

Use the proper helper to read the block device size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20211018101130.1838532-12-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/affs/super.c

@@ -389,7 +389,7 @@ static int affs_fill_super(struct super_block *sb, void *data, int silent)
 	 * blocks, we will have to change it.
 	 */
 
-	size = i_size_read(sb->s_bdev->bd_inode) >> 9;
+	size = bdev_nr_sectors(sb->s_bdev);
 	pr_debug("initial blocksize=%d, #blocks=%d\n", 512, size);
 
 	affs_set_blocksize(sb, PAGE_SIZE);