misc: Update release notes for v21.1.0.1 Hotfix

Change-Id: I8a99b2602b1fce566006a4e07aee8c3b574a6ae1
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/50030
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed