config: Fix need to set ISA of switch cpus.
config: Fix need to set ISA of switch cpus.

Since BaseCPU.createThreads() no longer overrides the BaseCPU.isa
parameter, switch_cpus should have the ISA copied. This fixes a
fatal error in BaseCPU when restoring from a checkpoint.

Change-Id: I4fdcacb76da46bdbe1ce37dcf05c5a6a8a9e5237
Signed-off-by: Austin Harris <f6ad0df4fda9699172cd7d1b24dbe00ad8828c61@utexas.edu>
Reviewed-on: https://gem5-review.googlesource.com/6241
Reviewed-by: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Maintainer: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>

gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,gem5/gem5,gem5/gem5,TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,gem5/gem5,TUD-OS/gem5-dtu,TUD-OS/gem5-dtu,gem5/gem5