Revise p4src documentation (#273)

- Remove old Linux Networking Recipe documentation from the
  p4src folder and replace it with a README file that links to
  the P4 Control Plane User Guide.

- Update Inline IPsec README file to link to the P4 Control Plane
  user guide.

Signed-off-by: Derek G Foster <[email protected]>

p4src/Inline_IPsec/README.md

@@ -1,21 +1,14 @@
 <!--
-/*
- * Copyright (c) 2022 Intel Corporation.
- *
- * SPDX-License-Identifier: Apache-2.0
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-- -->
+Copyright 2022-2023 Intel Corporation.
+SPDX-License-Identifier: Apache-2.0
+-->
 
-This is reference P4 program for Inline IPsec recipe.
+Inline IPsec Recipe
+===================
+
+Reference P4 program for the Inline IPsec recipe.
+
+See the [IPsec Offload](https://ipdk.io/p4cp-userguide/apps/ipsec-offload.html)
+section of the
+[P4 Control Plane User Guide](https://ipdk.io/p4cp-userguide/index.html)
+for more information.

p4src/linux_networking/README.md

@@ -0,0 +1,13 @@
+<!--
+Copyright 2023 Intel Corporation.
+SPDX-License-Identifier: Apache-2.0
+-->
+
+Linux Networking Recipe
+=======================
+
+See the
+[P4 Control Plane User Guide](https://ipdk.io/p4cp-userguide/index.html)
+for documentation of the
+[Linux Networking](https://ipdk.io/p4cp-userguide/apps/lnw/lnw-index.html)
+application.

p4src/linux_networking/dpdk/README.md

@@ -0,0 +1,15 @@
+<!--
+Copyright 2023 Intel Corporation.
+SPDX-License-Identifier: Apache-2.0
+-->
+
+Linux Networking Recipe (DPDK)
+==============================
+
+Reference P4 program for the Linux Networking recipe.
+
+See the [P4 Control Plane User Guide](https://ipdk.io/p4cp-userguide/index.html)
+for more information.
+
+- [Linux Networking for DPDK](https://ipdk.io/p4cp-userguide/apps/lnw/dpdk/dpdk-linux-networking.html)
+- [Linux Networking with ECMP (DPDK)](https://ipdk.io/p4cp-userguide/apps/lnw/dpdk/dpdk-linux-networking-ecmp.html)