ublk: Fix signedness bug returning warning

There are two warnings reported by smatch:

drivers/block/ublk_drv.c:445 ublk_setup_iod_zoned() warn:
	signedness bug returning '(-95)'
drivers/block/ublk_drv.c:963 ublk_setup_iod() warn:
	signedness bug returning '(-5)'

The type of "blk_status_t" is either be a u32 or u8, but this two
functions return a negative value when not supported or failed. Use
the error code of the blk module to fix these warnings.

Fixes: 29802d7c ("ublk: enable zoned storage support")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202308100201.TCRhgdvN-lkp@intel.com/Signed-off-by: Li Zetao <lizetao1@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230810084836.3535322-1-lizetao1@huawei.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/ublk_drv.c

@@ -442,7 +442,7 @@ static int ublk_revalidate_disk_zones(struct ublk_device *ub)
 static blk_status_t ublk_setup_iod_zoned(struct ublk_queue *ubq,
 					 struct request *req)
 {
-	return -EOPNOTSUPP;
+	return BLK_STS_NOTSUPP;
 }
 
 #endif
@@ -960,7 +960,7 @@ static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
 
 	if (!ublk_queue_is_zoned(ubq) &&
 	    (op_is_zone_mgmt(op) || op == REQ_OP_ZONE_APPEND))
-		return -EIO;
+		return BLK_STS_IOERR;
 
 	switch (req_op(req)) {
 	case REQ_OP_READ: