rbd: use bvec_virt

Use bvec_virt instead of open coding it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20210804095634.460779-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rbd.c

@@ -2986,8 +2986,7 @@ static bool is_zero_bvecs(struct bio_vec *bvecs, u32 bytes)
 	};
 
 	ceph_bvec_iter_advance_step(&it, bytes, ({
-		if (memchr_inv(page_address(bv.bv_page) + bv.bv_offset, 0,
-			       bv.bv_len))
+		if (memchr_inv(bvec_virt(&bv), 0, bv.bv_len))
 			return false;
 	}));
 	return true;