x86, olpc: Use device tree for platform identification

Make OLPC fully depend on device tree, and use it to identify the OLPC
platform details. Some nodes are exposed as platform devices where we
plan to use device tree for device probing.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
LKML-Reference: <20110313151017.C255F9D401E@zog.reactivated.net>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>