dcssblk: use bvec_virt

Use bvec_virt instead of open coding it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210804095634.460779-15-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/s390/block/dcssblk.c

@@ -892,8 +892,7 @@ dcssblk_submit_bio(struct bio *bio)
 
 	index = (bio->bi_iter.bi_sector >> 3);
 	bio_for_each_segment(bvec, bio, iter) {
-		page_addr = (unsigned long)
-			page_address(bvec.bv_page) + bvec.bv_offset;
+		page_addr = (unsigned long)bvec_virt(&bvec);
 		source_addr = dev_info->start + (index<<12) + bytes_done;
 		if (unlikely((page_addr & 4095) != 0) || (bvec.bv_len & 4095) != 0)
 			// More paranoia.