Added Odroid XU4 as another supported board

BANANAPI.md → Hardware.md

-# Setup BananaPI for benchmarking
+# Setup Hardware (Banana PI and Drdroid XU4) for benchmarking
 
 The goal of this documentation is to get a linux image running on a
 bananaPI board that allows for very isolated benchmarks showing full
@@ -6,9 +6,9 @@ time distributions of the measurement runs.
 
 ## Base Setup
 
-First step is to get a linux image running on the banana PI. We choose to use the
+First step is to get a linux image running on the hardware platforms. We choose to use the
 [armbian](https://www.armbian.com/) project as it is the only one with support for the
-bananaPI m3. For this we generally 
+both boards. For this we generally 
 [follow the instructions given](https://docs.armbian.com/Developer-Guide_Build-Preparation/),
 below are notes on what to do to get the rt kernel patch into it and to build.
 
@@ -23,19 +23,21 @@ General Setup:
 - `$ git clone --depth 1 https://github.com/armbian/build`
 - `$ cd build`
 - To verify the environment first go for a 'clean build' without patch: `# ./compile.sh` 
-- Select the bananaPI m3 board and a minimal console build
+- Select the bananaPI m3/odroid xu4 board and a minimal console build
+- NOTE: To this date, the legacy kernel (4.14.y) has to be selected for the odroid xu4 board 
 
 Apply RT Pach:
 - Find the current kernel version armbian is using, e.g. from the previous build logs
 - Download and unpack the matching rt path from https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/
 - You should have a single .patch file, place it in build/userpatches/kernel/sunix-current/patch-5.4.28-rt19.patch
 - Re-run the `# ./compile.sh` script
-- Select BananaPI M3, Command Line Minimal and SHOW KERNEL CONFIG
+- Select BananaPI M3/Odroid XU4, Command Line Minimal and SHOW KERNEL CONFIG
 - The build should pick up the patch (and show it in the logs)
 - You will be ask to fill in some settings. Choose (4) fully preemptive at the first option
 - Fill out the other asked settings to your liking. To avoid issues just leave them at default.
 - You will then be in the kernel config window
-- Here disable the file systems AUFS and NFS in the settings (they cause build issues and we do not need them)
+    - BananaPI: Here disable the file systems AUFS and NFS in the settings (they cause build issues and we do not need them)
+    - Odroid: Disable Heterogeneous Multi-Processing (HMP) in the settings (does not work with preempt_rt yet)
 - Store the settings and build the image
 - If successfull, the flashed image should show the preempt patch with `uname -a` and should have good latencies in cyclictest