util, arm: Support mmapped m5ops on aarch64

util, arm: Support mmapped m5ops on aarch64

Add support for memory-mapped m5ops in the aarch64 version of the m5
utility. To enable support for memory-mapped m5ops, compile the tool
with the define M5OP_ADDR set to the base of the m5op PA range.

Change-Id: I13e21e48536b9849bf4081411b66b2f350f7a8ac
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2966