tests: Use default None argument in makeArmSystem

JIRA: https://gem5.atlassian.net/browse/GEM5-387

Change-Id: I18b1ed360b2d285e4df19b896e692356ef6f8819
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30219
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabeblack@google.com>

tests/configs/arm_generic.py

@@ -100,7 +100,7 @@ class LinuxArmSystemBuilder(object):
         sc = SysConfig(None, self.mem_size, [disk_image], "/dev/sda")
         system = FSConfig.makeArmSystem(self.mem_mode,
                                         self.machine_type, self.num_cpus,
-                                        sc, False, ruby=self.use_ruby)
+                                        sc, ruby=self.use_ruby)
 
         # We typically want the simulator to panic if the kernel
         # panics or oopses. This prevents the simulator from running