block: add a loff_t cast to bdev_nr_bytes

Not really needed as both loff_t and sector_t are always 64-bits wide,
but this documents the different types a bit better.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211104172037.531803-1-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/genhd.h

@@ -243,7 +243,7 @@ static inline sector_t bdev_nr_sectors(struct block_device *bdev)
 
 static inline loff_t bdev_nr_bytes(struct block_device *bdev)
 {
-	return bdev_nr_sectors(bdev) << SECTOR_SHIFT;
+	return (loff_t)bdev_nr_sectors(bdev) << SECTOR_SHIFT;
 }
 
 static inline sector_t get_capacity(struct gendisk *disk)