mem-ruby: Use CircularQueue for prefetcher's unit filter

mem-ruby: Use CircularQueue for prefetcher's unit filter

Ruby prefetcher's unit filter is a circular queue, so use the class
created for this functionality.

This changes the behavior, since previously iterating through the
filter was completely arbitrary, and now it iterates from the
beginning of the queue to the end when accessing and updating
the filter's contents.

Change-Id: I834be88a33580d5857c38e9bae8b289c5a6250b9
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24532
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>