mem-cache: Add a masked pattern to compressors

mem-cache: Add a masked pattern to compressors

The masked pattern compares masked values to masked dictionary entries
to determine whether these values match. If successful, the bits that
do not match must be added to the compressed data.

Change-Id: I4b1c8feb0faa99576382b54a73a20c353f965d2a
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21150
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>