cpu: Add CpuCluster method to allow querying the number of CPUs.

Add a `__len__` method to `CpuCluster` to allow clients to query the
number of CPUs.

Change-Id: I6fe680423ed6fc301faaf75b8685b080a4774fef
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/69678
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
1 file changed