bnxt_en: Remove debugfs when pci_register_driver failed

When pci_register_driver failed, we need to remove debugfs,
which will caused a resource leak, fix it.

Resource leak logs as follows:
[   52.184456] debugfs: Directory 'bnxt_en' with parent '/' already present!

Fixes: cabfb09 ("bnxt_en: add debugfs support for DIM")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -14037,8 +14037,16 @@ static struct pci_driver bnxt_pci_driver = {
 
 static int __init bnxt_init(void)
 {
+	int err;
+
 	bnxt_debug_init();
-	return pci_register_driver(&bnxt_pci_driver);
+	err = pci_register_driver(&bnxt_pci_driver);
+	if (err) {
+		bnxt_debug_exit();
+		return err;
+	}
+
+	return 0;
 }
 
 static void __exit bnxt_exit(void)