ArmVirtPkg/ArmVirtQemu: Add RngDxe driver

Add the RngDxe driver to the build, backed by either RNDR or TRNG, one
of which is expected to be available in most cases:
- RNDR is implemented by the 'max' CPU that QEMU implements in TCG mode
- TRNG is implemented by the KVM hypervisor, which backs QEMU's 'host'
  CPU

Other TCG modes (e.g., the 'cortex-a*' CPUs) implement neither, which
should prevent the RngDxe driver from dispatching entirely, resulting
in the same situation as before.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>

Committed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Doug Flick [MSFT] <doug.edk2@gmail.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

ArmVirtPkg/ArmVirtQemuFvMain.fdf.inc

@@ -75,6 +75,7 @@ READ_LOCK_STATUS   = TRUE
   INF ArmPkg/Drivers/TimerDxe/TimerDxe.inf
   INF OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf
   INF MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
+  INF SecurityPkg/RandomNumberGenerator/RngDxe/RngDxe.inf
 
   #
   # FAT filesystem + GPT/MBR partitioning + UDF filesystem + virtio-fs