vepxress64: add guide for running FVP with TF-A

Add documentation on how to run FVP with U-Boot and TF-A. This helps
users configure and run U-Boot correctly on Arm models.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
1 file changed