configs/rdn2: Add ArmVirtKvmTool to rdn2 UEFI package list

Define and add ArmVirtKvmTool package to the existing list of RD-N2
UEFI packages to build and provide firmware that can be used for UEFI
based guest OS boot in a virtualized environment created with the help
of kvmtool and linux KVM.
Also define EDK2_OUT_DIR flag to point to the output directory to
build ArmVirtKvmTool as current build-scripts don't create any
ArmVirtKvmTool-$(ARCH) output directory.

Signed-off-by: Sathyam Panda <sathyam.panda@arm.com>
Suggested-by: Thomas Abraham <thomas.abraham@arm.com>
Change-Id: I87baf891d3f658bcb9b6a645a64391b891cddbb3