dev-arm: Use recurseDeviceTree instead of custom in platform

dev-arm: Use recurseDeviceTree instead of custom in platform

The platform code uses a custom mechanism to traverse the object
hierarchy when generating device trees. This is highly undesirable
since this breaks for common cases such as when SimObjects are stored
in a list.

Change-Id: I1b968e5fa1db62f1456e3c0ac3de47ab1299e58d
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10781
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>