sconfig: rename lapic_cluster -> cpu_cluster

The name lapic_cluster is a bit misleading, since the construct is not local
APIC specific by concept. As implementations and hardware change, be more
generic about our naming. This will allow us to support non-x86 systems without
adding new keywords.

Change-Id: Icd7f5fcf6f54d242eabb5e14ee151eec8d6cceb1
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/2377
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/mainboard/ibm/e325/devicetree.cb

@@ -1,5 +1,5 @@
 chip northbridge/amd/amdk8/root_complex
-	device lapic_cluster 0 on
+	device cpu_cluster 0 on
 		chip cpu/amd/socket_940
 			device lapic 0 on end
 		end

src/mainboard/ibm/e326/devicetree.cb

@@ -1,5 +1,5 @@
 chip northbridge/amd/amdk8/root_complex
-	device lapic_cluster 0 on
+	device cpu_cluster 0 on
 		chip cpu/amd/socket_940
 			device lapic 0 on end
 		end