misc: Update the version to v21.1.0.0

Change-Id: I4174611bdaf68673f77a446e979776ad502ae20b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48583
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
3 files changed