util: Removed libelf-dev dep from Dockerfiles

The libelf-dev dependency is no longer required in our Dockerfiles.

This reverts commit 0cf67fb36281b17956d4dc10f05054bf711b4ba3,
https://gem5-review.googlesource.com/c/public/gem5/+/33596.

The libelf-dev dependency has been kept for the "all_dependencies"
Dockerfiles.

The corresponding Docker images have been built and uploaded to:
https://gcr.io/gem5-test.

Change-Id: Iacbd8240f69d476ad3a649baaccb6b85fec2487c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34676
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
diff --git a/util/dockerfiles/gcn-gpu/Dockerfile b/util/dockerfiles/gcn-gpu/Dockerfile
index 065dad6..d0fe759 100644
--- a/util/dockerfiles/gcn-gpu/Dockerfile
+++ b/util/dockerfiles/gcn-gpu/Dockerfile
@@ -34,8 +34,7 @@
     libboost-filesystem-dev \
     libboost-system-dev \
     libboost-dev \
-    libpng12-dev \
-    libelf-dev
+    libpng12-dev
 
 RUN python -m pip install -U pip && \
     python -m pip install -U setuptools scons
diff --git a/util/dockerfiles/ubuntu-18.04_clang-version/Dockerfile b/util/dockerfiles/ubuntu-18.04_clang-version/Dockerfile
index b98af88..428bd02 100644
--- a/util/dockerfiles/ubuntu-18.04_clang-version/Dockerfile
+++ b/util/dockerfiles/ubuntu-18.04_clang-version/Dockerfile
@@ -40,7 +40,7 @@
 RUN apt -y upgrade
 RUN apt -y install git m4 scons zlib1g zlib1g-dev clang-${version} \
     libprotobuf-dev protobuf-compiler libprotoc-dev libgoogle-perftools-dev \
-    python-dev python python-six doxygen libelf-dev
+    python-dev python python-six doxygen
 
 RUN apt-get --purge -y remove gcc
 
diff --git a/util/dockerfiles/ubuntu-18.04_gcc-version/Dockerfile b/util/dockerfiles/ubuntu-18.04_gcc-version/Dockerfile
index 5eb40b1..902e4a0 100644
--- a/util/dockerfiles/ubuntu-18.04_gcc-version/Dockerfile
+++ b/util/dockerfiles/ubuntu-18.04_gcc-version/Dockerfile
@@ -37,8 +37,7 @@
 RUN apt -y upgrade
 RUN apt -y install git m4 scons zlib1g zlib1g-dev gcc-multilib \
     libprotobuf-dev protobuf-compiler libprotoc-dev libgoogle-perftools-dev \
-    python-dev python python-six doxygen wget zip gcc-${version} \
-    g++-${version} libelf-dev
+    python-dev python python-six doxygen wget zip gcc-${version} g++-${version}
 
 RUN update-alternatives --install \
     /usr/bin/g++ g++ /usr/bin/g++-${version} 100
diff --git a/util/dockerfiles/ubuntu-18.04_min-dependencies/Dockerfile b/util/dockerfiles/ubuntu-18.04_min-dependencies/Dockerfile
index f55ea2d..986b2b6 100644
--- a/util/dockerfiles/ubuntu-18.04_min-dependencies/Dockerfile
+++ b/util/dockerfiles/ubuntu-18.04_min-dependencies/Dockerfile
@@ -29,4 +29,4 @@
 RUN apt -y update
 RUN apt -y upgrade
 RUN apt -y install build-essential scons zlib1g-dev m4 python-dev python \
-    python-six libelf-dev
+    python-six
diff --git a/util/dockerfiles/ubuntu-20.04_gcc-version/Dockerfile b/util/dockerfiles/ubuntu-20.04_gcc-version/Dockerfile
index d952183..d2008b6 100644
--- a/util/dockerfiles/ubuntu-20.04_gcc-version/Dockerfile
+++ b/util/dockerfiles/ubuntu-20.04_gcc-version/Dockerfile
@@ -38,7 +38,7 @@
 RUN apt -y install git m4 scons zlib1g zlib1g-dev libprotobuf-dev \
     protobuf-compiler libprotoc-dev libgoogle-perftools-dev python3-dev \
     python3-six python-is-python3 doxygen libboost-all-dev libhdf5-serial-dev \
-    python3-pydot libpng-dev gcc-${version} g++-${version} libelf-dev
+    python3-pydot libpng-dev gcc-${version} g++-${version}
 
 RUN update-alternatives --install \
     /usr/bin/g++ g++ /usr/bin/g++-${version} 100