configs,arch,sim: Move fixFuncEventAddr into the Workload class.

configs,arch,sim: Move fixFuncEventAddr into the Workload class.

This is specialized per arch, and the Workload class is the only thing
actually using it. It doesn't make any sense to dispatch those calls
over to the System object, especially since that was, in most cases,
the only reason an ISA specific system class even still existed.

After this change, only ARM still has an architecture specific System
class.

Change-Id: I81b6c4db14b612bff8840157cfc56393370095e2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24287
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>