python: Don't assume SimObjects live in the global namespace

The importer in Python 3 doesn't like the way we import SimObjects
from the global namespace. Convert the existing SimObject declarations
to import from m5.objects. As a side-effect, this makes these files
consistent with configuration files.

Change-Id: I11153502b430822130722839e1fa767b82a027aa
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15981
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

src/cpu/simple/BaseSimpleCPU.py

@@ -30,9 +30,10 @@ from __future__ import print_function
 
 from m5.defines import buildEnv
 from m5.params import *
-from BaseCPU import BaseCPU
-from DummyChecker import DummyChecker
-from BranchPredictor import *
+
+from m5.objects.BaseCPU import BaseCPU
+from m5.objects.DummyChecker import DummyChecker
+from m5.objects.BranchPredictor import *
 
 class BaseSimpleCPU(BaseCPU):
     type = 'BaseSimpleCPU'
@@ -41,7 +42,7 @@ class BaseSimpleCPU(BaseCPU):
 
     def addCheckerCpu(self):
         if buildEnv['TARGET_ISA'] in ['arm']:
-            from ArmTLB import ArmTLB
+            from m5.objects.ArmTLB import ArmTLB
 
             self.checker = DummyChecker(workload = self.workload)
             self.checker.itb = ArmTLB(size = self.itb.size)