[POWERPC] Fix bus probe on Bamboo board

Commit 804ace88 changed the behavior of how compatible nodes are found.
This highlighted a bug on the Bamboo board where it wasn't probing the bus
specified in the DTS file.  We fix it by being explicit about which bus to
probe.
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Acked-by: David Gibson <david@gibson.dropbvear.id.au>

arch/powerpc/platforms/44x/bamboo.c

@@ -23,7 +23,7 @@
 #include "44x.h"
 
 static struct of_device_id bamboo_of_bus[] = {
-	{ .compatible = "ibm,plb", },
+	{ .compatible = "ibm,plb4", },
 	{ .compatible = "ibm,opb", },
 	{ .compatible = "ibm,ebc", },
 	{},