stdlib: Added LupioRNG to LupVBoard

This adds the LupioRNG device to our LupVBoard, adding
random number generation capability to this RISC-V
based system.

Change-Id: I89c78c119a46cc7b056005d8abef16b1816ee4c4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/53030
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>