cpu: Apply the ARM TLB rework to the checker CPU.

cpu: Apply the ARM TLB rework to the checker CPU.

The TLBs now create the stage 2 MMUs as children, and since those are
specialized for instruction and data, the CPU needs to use ArmITB or
ArmDTB instead of ArmTLB which is the base class without an MMU. This
was changed for the BaseCPU already, but the TLBs are added in the
checker CPU as well.

Change-Id: Ide8ce950622b40f69c37bbe2ea0d22295b76d7a6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21979
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>