aemfvp-a-rme: enabling uefi build for aemfvp-a-rme

Changes include
- UEFI_RME_BUILD_ENABLED flag to include building UEFI firmware and packing
  necessary binaries and firmware for boot.
- enable building ArmVirtKvmTool in UEFI to build the firmware for kvmtool
based virtual machines.
- enabling building ArmVExpress-FVP-AArch64 in UEFI to build the firmware
  to boot at FVP.
- build TF-A fip_uefi and bl1_uefi with FVP_AARCH64_EFI.fd
- added necessary TF-A build flags.
- generating and packing KVMTOOL_EFI for uefi boot of a distro image.

Signed-off-by: nitin sharma <nitin.sharma3@arm.com>
Change-Id: I634551f2bd131e1987eeeecc429aabd26ab5ded3