aemfvp-rme-a: Move the fvp model execution command to boot.sh

Move the fvp model execution command from run_model.sh to boot.sh.
Having it in the boot.sh helps to add more test runs/scenarios.

Change-Id: I010ad2a11c553f2d5ff14b423559282ae069d321
Signed-off-by: Dilip Kota <dilip.kota@arm.com>