mem-cache: Add a masked const value pattern to compressors

mem-cache: Add a masked const value pattern to compressors

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

Change-Id: I4c53568694dab916136fe384cb2ee10e554f7136
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21151
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>