arch,sim: Replace setuidFunc with ignoreFunc.

arch,sim: Replace setuidFunc with ignoreFunc.

The setuidFunc just ignores the call and warns about it, and that's
what ignoreFunc already does.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-187

Change-Id: I7655863ed6fe200ff3ac087be3218d49c3c43061
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23194
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>