configs: Fix FastmodelCluster cpu initialization

We should create the thread and the interrupt controller of fastmodel by
calling the create function explicitly.

Change-Id: I269440e144e83fa0a31d8cdf285fed31642f4f73
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36380
Reviewed-by: Earl Ou <shunhsingou@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/arm/devices.py

@@ -258,6 +258,8 @@ class FastmodelCluster(SubSystem):
             core.semihosting_enable = False
             core.RVBARADDR = 0x10
             core.redistributor = gic.redistributor
+            core.createThreads()
+            core.createInterruptController()
         self.cpus = [ cpu ]
 
         a2t = AmbaToTlmBridge64(amba=cpu.amba)