cpu: change the location of BTBlookup

cpu: change the location of BTBlookup

BTBlookup should be done only if BTB is used, previously
this stat was updated for indirector predictor as well.

https: //gem5.atlassian.net/browse/GEM5-338
Change-Id: I20695dc7a8677d4fd0c4ae9f4f7d279387d5ad62
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25625
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Ayaz Akram <yazakram@ucdavis.edu>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>