gpu-compute: Delete code related to X86PagetableWalker in X86GPUTLB.py.

This code will never be executed since FULL_SYSTEM is not part of the
build environment (and hasn't been for many years), and on top of that,
this declaration redundantly (and incompletely) tries to set up the
X86PagetableWalker that the ISA already sets up.

Change-Id: I40cffbd7f60c1f741b1a14d9009f80185c9ce28c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49405
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>

src/gpu-compute/X86GPUTLB.py

@@ -36,13 +36,6 @@ from m5.proxy import *
 from m5.objects.ClockedObject import ClockedObject
 from m5.SimObject import SimObject
 
-if buildEnv.get('FULL_SYSTEM', False):
-    class X86PagetableWalker(SimObject):
-        type = 'X86PagetableWalker'
-        cxx_class = 'gem5::X86ISA::Walker'
-        port = ResponsePort("Port for the hardware table walker")
-        system = Param.System(Parent.any, "system object")
-
 class X86GPUTLB(ClockedObject):
     type = 'X86GPUTLB'
     cxx_class = 'gem5::X86ISA::GpuTLB'