nvme-core: rework a NQN copying operation

Although it is easy to see that the code in nvme_init_subnqn() guarantees that
the subsys->nqn string is '\0'-terminated, apparently Coverity is not smart
enough to see this. Make it easier for Coverity to analyze this code by changing
the strncpy() call into a strlcpy() call. This patch does not change the
behavior of the code but fixes Coveritiy ID 1423720.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -2076,7 +2076,7 @@ static void nvme_init_subnqn(struct nvme_subsystem *subsys, struct nvme_ctrl *ct
 
 	nqnlen = strnlen(id->subnqn, NVMF_NQN_SIZE);
 	if (nqnlen > 0 && nqnlen < NVMF_NQN_SIZE) {
-		strncpy(subsys->subnqn, id->subnqn, NVMF_NQN_SIZE);
+		strlcpy(subsys->subnqn, id->subnqn, NVMF_NQN_SIZE);
 		return;
 	}