base: Add warn_if_once macro
base: Add warn_if_once macro

Change-Id: Ie68f3b07a35ed2e6b0eee20b3b34050542fcdc6c
Signed-off-by: Tiago Muck <02f879f33eea3aaf6781160757a59709a6f01bed@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18420
Reviewed-by: Brandon Potter <0c4047814a967fe28855a3d9d73d9b4959444c57@amd.com>
Reviewed-by: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Reviewed-by: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Maintainer: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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