partitions/efi: use bdev_nr_bytes instead of open coding it

Use the proper helper to read the block device size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211019062024.2171074-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/partitions/efi.c

@@ -133,7 +133,7 @@ efi_crc32(const void *buf, unsigned long len)
  */
 static u64 last_lba(struct gendisk *disk)
 {
-	return div_u64(disk->part0->bd_inode->i_size,
+	return div_u64(bdev_nr_bytes(disk->part0),
 		       queue_logical_block_size(disk->queue)) - 1ULL;
 }