Add fvp.md

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
Reviewed-by: Igor Opaniuk <igor.opaniuk@linaro.org>

devices/fvp.md

+# OP-TEE on Foundation Models / FVP
+
+# Contents
+1. [Introduction](#1-introduction)
+2. [Regular build](#2-regular-build)
+
+# 1. Introduction
+The instructions here will tell how to run OP-TEE using Foundation Models.
+
+# 2. Regular build
+Start out by following the "Get and build the solution" in the [README.md] file,
+but before trying to actually run the solution you must first obtain the
+[Foundation Models binaries]. That binary should be untar'ed to the root of the
+repo forest. I.e., the folder named `Foundation_Platformpkg` must be in the root.
+When this pre-condition has been done, then you can simply continue with
+```bash
+$ make run
+```
+And the FVP should build the root fs and then start the simulation.
+
+[Foundation Models binaries]: https://developer.arm.com/products/system-design/fixed-virtual-platforms
+[README.md]: https://github.com/OP-TEE/build/README.md