aemfvp-a-rme: Script to run tftf standard test suite

Add changes to boot the FVP with boot loaders and TF-A
firmware and execute the  tftf standard test suite.

This patch also introduces changes to populate the FVP
model parameters with Linux and File system paths only
when respective strings are non zero.

Change-Id: I9ddc61e57f8ace4898a58000822937b4511f2d7f
Signed-off-by: Dilip Kota <dilip.kota@arm.com>