mm/vmscan: print err before panic

If panic is enable,the err information will not be printed before bugon,
So swap it.  Print the return value of PTR_ERR(pgdat->kswapd) also.

Link: https://lkml.kernel.org/r/20230906083700.181-1-angus.chen@jaguarmicro.comSigned-off-by: Angus Chen <angus.chen@jaguarmicro.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -7892,8 +7892,9 @@ void __meminit kswapd_run(int nid)
 		pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
 		if (IS_ERR(pgdat->kswapd)) {
 			/* failure at boot is fatal */
+			pr_err("Failed to start kswapd on node %d，ret=%ld\n",
+				   nid, PTR_ERR(pgdat->kswapd));
 			BUG_ON(system_state < SYSTEM_RUNNING);
-			pr_err("Failed to start kswapd on node %d\n", nid);
 			pgdat->kswapd = NULL;
 		}
 	}