dpdk: update branch for Gatekeeper v1.2

This new branch for Gatekeeper v1.2 is based on DPDK v21.05.
The motivation for this new branch is to solve the LACP disconnect bug
(see the DPDK commit
DPDK/dpdk@fad80ab
).
DPDK v21.05 is the first DPDK release to include the referred commit.

This commit also adds the package python3-pyelftools as a dependency.

.github/workflows/c-cpp.yml

@@ -27,7 +27,8 @@ jobs:
         libhugetlbfs-bin build-essential gcc-multilib linux-headers-`uname -r`
         libmnl0 libmnl-dev libkmod2 libkmod-dev libnuma-dev libelf1 libelf-dev
         libc6-dev-i386 autoconf flex bison libncurses5-dev libreadline-dev
-        python libcap-dev libcap2 meson ninja-build pkg-config
+        python python3-pyelftools libcap-dev libcap2 meson ninja-build
+        pkg-config
 
     - name: Setup Gatekeeper
       run: sudo ./setup.sh

.gitmodules

@@ -1,7 +1,7 @@
 [submodule "dependencies/dpdk"]
 	path = dependencies/dpdk
 	url = https://github.com/cjdoucette/dpdk
-	branch = gkv1.2
+	branch = gkv1.2b
 [submodule "dependencies/luajit-2.0"]
 	path = dependencies/luajit-2.0
 	url = https://github.com/AltraMayor/luajit.git

README.md

@@ -204,7 +204,8 @@ the folder `bpf/`.
 The `autoconf`, `flex`, `bison`, `libncurses5-dev`, and
 `libreadline-dev` packages are for BIRD. The `devscripts` package is used to
 build Gatekeeper Debian packages.
-`python` is needed to be able to run the `dpdk-devbind.py` script.
+The packages `python` and `python3-pyelftools` are needed to build DPDK and to
+run Python scripts such as `dpdk-devbind.py`.
 `libcap-dev` is needed to compile Gatekeeper, but only `libcap2` is needed
 to run Gatekeeper.
 `meson` and `ninja-build` are needed for building DPDK.