dev-arm, configs: Using _on_chip_memory for on chip memory

This patch is pulling the on-chip memory outside of the on_chip_devices
list.
The external interface will be more or less the same: configuration
scripts will still use the attachOnChipIO method; a new kw argument has
been added in order to store mem_ports.

We want to provide to on-chip memory the same mechanism used when
collecting on-chip dma ports. This is needed when using Ruby, since
we need to pass a non None mem_ports to prevent the bootmem to be
wired to the bus.

Change-Id: Ifc519c3072dc5de1530772c70c80dc2094e2c54c
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22000
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/common/FSConfig.py

@@ -365,7 +365,9 @@ def makeArmSystem(mem_mode, machine_type, num_cpus=1, mdesc=None,
         self.realview.attachIO(self.iobus)
     elif ruby:
         self._dma_ports = [ ]
-        self.realview.attachOnChipIO(self.iobus, dma_ports=self._dma_ports)
+        self._mem_ports = [ ]
+        self.realview.attachOnChipIO(self.iobus,
+            dma_ports=self._dma_ports, mem_ports=self._mem_ports)
         self.realview.attachIO(self.iobus, dma_ports=self._dma_ports)
     else:
         self.realview.attachOnChipIO(self.membus, self.bridge)