tty: rpmsg: Assign returned id to a local variable

Instead of putting garbage in the data structure, assign allocated id
or an error code to a temporary variable. This makes code cleaner.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211025135148.53944-1-andriy.shevchenko@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/rpmsg_tty.c

@@ -121,15 +121,16 @@ static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
 		return ERR_PTR(-ENOMEM);
 
 	mutex_lock(&idr_lock);
-	cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
+	err = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
 	mutex_unlock(&idr_lock);
 
-	if (cport->id < 0) {
-		err = cport->id;
+	if (err < 0) {
 		kfree(cport);
 		return ERR_PTR(err);
 	}
 
+	cport->id = err;
+
 	return cport;
 }