Reported smatch warning:
drivers/block/mtip32xx/mtip32xx.c:4163 mtip_block_shutdown() warn: variable dereferenced before check 'dd->disk' (see line 4159)

dd->disk->disk_name accessed before the check if dd->disk is NULL. Fixed this
and access of dd->queue/dd->disk->queue.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NAsai Thambi S P <asamymuthupa@micron.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>