sim,configs: Default m5ops_base to 0 (disabled) on x86.

This is already the default for other platforms. This is most important
when using KVM, where this mechanism is the only way to trigger pseudo
instructions, or in SE mode to also trigger system calls.

Change-Id: I0094e6814898ba397c7425e0fe76d84853bb17ad
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52498
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/gem5/components/boards/x86_board.py

@@ -99,6 +99,8 @@ class X86Board(AbstractBoard, KernelDiskWorkload):
         # Set up all of the I/O.
         self._setup_io_devices()
 
+        self.m5ops_base = 0xffff0000
+
     def _setup_io_devices(self):
         """ Sets up the x86 IO devices.