tests: Update the cpu_tests download URL
tests: Update the cpu_tests download URL

This new URL puts the binaries in the same directory structure as the
other test programs. This is part of a minor re-arrange of the Google
Cloud bucket.

Change-Id: Ibbd1385adf96bc63b54b717b5385c77a6b0c4dbb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54465
Reviewed-by: Bobby Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Maintainer: Bobby Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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