mem: Use using to expose a print method that would otherwise be hidden.
mem: Use using to expose a print method that would otherwise be hidden.

This method would be hidden in the subclass which upset clang 11, and
that caused the build to break.

Change-Id: Ie678fc96a26809eb8f2acd0bddc1df81c0a9aa1e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25227
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5