skd: fix error return code in skd_pci_probe()

Fix to return -ENOMEM in the skd construct error handling
case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>