icnss2: return '-EAGAIN' when wlan driver load request comes too early

Sometimes wlan driver loading comes very early, icnss2
driver is not ready at that point and returns '-ENODEV',
which results in wlan failure.

To fix it, icnss2 returns '-EAGAIN' in such case to
trigger the retry mechanism in wlan driver.

Change-Id: Ia9f955622d052842ecd1fe1a752fd20d1e98804c
CRs-Fixed: 3851180

icnss2/main.c

@@ -3103,7 +3103,8 @@ int __icnss_register_driver(struct icnss_driver_ops *ops,
 	struct icnss_priv *priv = icnss_get_plat_priv();
 
 	if (!priv || !priv->pdev) {
-		ret = -ENODEV;
+		icnss_pr_vdbg("icnss2 is not ready for register driver\n");
+		ret = -EAGAIN;
 		goto out;
 	}