net/bnxt: fix null dereference in session cleanup

In tf_session_create(), there is a case that with 'tfp->session' still
be NULL and run 'goto cleanup', which will leads to a null dereference
by 'tfp_free(tfp->session->core_data)' in the cleanup.

Fixes: a46bbb5 ("net/bnxt: update multi device design")
Cc: stable@dpdk.org

Signed-off-by: Weiguo Li <liwg06@foxmail.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>

drivers/net/bnxt/tf_core/tf_session.c

@@ -230,10 +230,12 @@ tf_session_create(struct tf *tfp,
 			    "FW Session close failed, rc:%s\n",
 			    strerror(-rc));
 	}
+	if (tfp->session) {
+		tfp_free(tfp->session->core_data);
+		tfp_free(tfp->session);
+		tfp->session = NULL;
+	}
 
-	tfp_free(tfp->session->core_data);
-	tfp_free(tfp->session);
-	tfp->session = NULL;
 	return rc;
 }