cpu: move initCPU calls from initState to init

cpu: move initCPU calls from initState to init

This commit moves the initCPU calls from initState to init
of base cpu (which were added in commit 0b8d02dec492215aa).
This is a temporary fix to solve the problem of X86System
initState getting called before initState of base cpu.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-292

Change-Id: I7434cd811536175562cfa2646f4326907fadad8c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24884
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>