cpu,mem: Converting stats to supported units

There are several stats having unit being a multiple of supported
units. This change makes the following conversions:
  * MiB/s -> bytes/s
  * percentage -> ratio

Change-Id: I9832796e87698daa7f87f91fa39ce40bbf92e737
Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41013
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>