mem-cache: Limit compression size

mem-cache: Limit compression size

Add a threshold so that if the compressed size is greater than it,
the compression is abandoned, and the data is considered uncompressible.

Change-Id: Ic416195b06ec440a40263b75bd0f0383cde2ea6a
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21144
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>