Platform: Add support for MPS2 AN539 FPGA board

Adds AN539 platform support files. Adds a new target platform to
the build system: "AN539".

Change-Id: I27336502f9526b0e5476d0d594c2d24fb73e72dc
Signed-off-by: Marton Berke <marton.berke@arm.com>
71 files changed