virt: acrn: replace deprecated strncpy with strscpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We can see that client->name should be NUL-terminated based on its usage
with a %s C-string format specifier.
|	client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
|					client->vm->vmid, client->name);

NUL-padding is not required as client is already zero-allocated:
|	client = kzalloc(sizeof(*client), GFP_KERNEL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Note that this patch relies on the _new_ 2-argument version of strscpy()
introduced in Commit e6584c3 ("string: Allow 2-argument
strscpy()").

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: KSPP#90
Cc:  <linux-hardening@vger.kernel.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240320-strncpy-drivers-virt-acrn-ioreq-c-v1-1-db6996770341@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>

Author: JustinStitt

drivers/virt/acrn/ioreq.c

@@ -433,7 +433,7 @@ struct acrn_ioreq_client *acrn_ioreq_client_create(struct acrn_vm *vm,
 	client->priv = priv;
 	client->is_default = is_default;
 	if (name)
-		strncpy(client->name, name, sizeof(client->name) - 1);
+		strscpy(client->name, name);
 	rwlock_init(&client->range_lock);
 	INIT_LIST_HEAD(&client->range_list);
 	init_waitqueue_head(&client->wq);