nbd: Use blk_validate_block_size() to validate block size

Use the block layer helper to validate block size instead
of open coding it.
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Link: https://lore.kernel.org/r/20211026144015.188-3-xieyongji@bytedance.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/nbd.c

@@ -315,7 +315,8 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize,
 {
 	if (!blksize)
 		blksize = 1u << NBD_DEF_BLKSIZE_BITS;
-	if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize))
+
+	if (blk_validate_block_size(blksize))
 		return -EINVAL;
 
 	nbd->config->bytesize = bytesize;