powerpc/85xx: Minor fixes for 85xxds and 8536ds board.

Remove the "uninitialized use" compile warning and avoid potential
runtime issue.
Signed-off-by: Jason Jin <Jason.jin@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/platforms/85xx/mpc8536_ds.c

@@ -36,7 +36,7 @@ void __init mpc8536_ds_pic_init(void)
 	struct resource r;
 	struct device_node *np;
 
-	np = of_find_node_by_type(np, "open-pic");
+	np = of_find_node_by_type(NULL, "open-pic");
 	if (np == NULL) {
 		printk(KERN_ERR "Could not find open-pic node\n");
 		return;

arch/powerpc/platforms/85xx/mpc85xx_ds.c

@@ -64,7 +64,7 @@ void __init mpc85xx_ds_pic_init(void)
 	int cascade_irq;
 #endif
 
-	np = of_find_node_by_type(np, "open-pic");
+	np = of_find_node_by_type(NULL, "open-pic");
 	if (np == NULL) {
 		printk(KERN_ERR "Could not find open-pic node\n");
 		return;