mem-ruby: fixes for masked writes

mem-ruby: fixes for masked writes

This adds DataBlock::setData(PacketPtr) to update the block with
packet data. The method uses the packet's writeData to copy the
correct bytes if the request is a masked write.

Change-Id: I9e5f70fed29edcf55fef94a4b145aa838dc60eac
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41134
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>