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/gpu-compute/GPU.py

@@ -33,16 +33,17 @@
 #  Author: Steve Reinhardt
 #
 
-from ClockedObject import ClockedObject
-from Device import DmaDevice
 from m5.defines import buildEnv
 from m5.params import *
 from m5.proxy import *
 from m5.SimObject import SimObject
-from MemObject import MemObject
-from Process import EmulatedDriver
-from Bridge import Bridge
-from LdsState import LdsState
+
+from m5.objects.ClockedObject import ClockedObject
+from m5.objects.Device import DmaDevice
+from m5.objects.MemObject import MemObject
+from m5.objects.Process import EmulatedDriver
+from m5.objects.Bridge import Bridge
+from m5.objects.LdsState import LdsState
 
 class PrefetchType(Enum): vals = [
     'PF_CU',

src/gpu-compute/LdsState.py

@@ -35,7 +35,7 @@ from m5.defines import buildEnv
 from m5.params import *
 from m5.proxy import *
 
-from MemObject import MemObject
+from m5.objects.MemObject import MemObject
 
 class LdsState(MemObject):
     type = 'LdsState'