x86, olpc: Rework BIOS signature check

The XO-1.5 laptop is not currently detected as an OLPC machine because
it fails this XO-1-centric check.

Now that we have OLPC OFW support in the kernel, a more sensible
check is to see if we found OFW during boot and check the architecture
property.

Also remove a now-meaningless codepath, as we're always going to have
OFW support with OLPC.

Signed-off-by: Daniel Drake <dsd@laptop.org>
LKML-Reference: <20100923162846.D8D409D401B@zog.reactivated.net>
Cc: Andres Salomon <dilinger@queued.net>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/olpc_ofw.c b/arch/x86/kernel/olpc_ofw.c
index 3218aa7..7873204 100644
--- a/arch/x86/kernel/olpc_ofw.c
+++ b/arch/x86/kernel/olpc_ofw.c
@@ -74,6 +74,12 @@
 }
 EXPORT_SYMBOL_GPL(__olpc_ofw);
 
+bool olpc_ofw_present(void)
+{
+	return olpc_ofw_cif != NULL;
+}
+EXPORT_SYMBOL_GPL(olpc_ofw_present);
+
 /* OFW cif _should_ be above this address */
 #define OFW_MIN 0xff000000