docs: armv8-R aarch64 fvp_r documentation

Documenting armv8-R aarch64 fvp_r features, boot sequence, and build
procedure.

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: If75d59acdf0f8a61cea6187967a4c35af2f31c98
2 files changed