checker: make checker cpu id match its host's cpu id

when using the checker i ran into problems where an instruction reading the
cpu id register failed because the ids did not match, and hence, the result
of the instruction did not match. this patch ensures that the ids match so
this instruction does not fail. this problem only seemed to manifest itself
when multiple cores were in the system, either multi-core, or extra switched-
out cores present in the system.

src/cpu/o3/O3CPU.py

@@ -141,6 +141,7 @@ class DerivO3CPU(BaseCPU):
                                      warnOnlyOnLoadError=True)
             self.checker.itb = ArmTLB(size = self.itb.size)
             self.checker.dtb = ArmTLB(size = self.dtb.size)
+            self.checker.cpu_id = self.cpu_id
 
         else:
             print "ERROR: Checker only supported under ARM ISA!"