powerpc/mpic: Search for open-pic device-tree node if NULL

Almost all PowerPC platforms use a standard "open-pic" device node so
the mpic_alloc() function now accepts NULL for the device-node.  This
will cause it to perform a default search with of_find_matching_node().

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/85xx/p1010rdb.c

@@ -32,16 +32,8 @@
 
 void __init p1010_rdb_pic_init(void)
 {
-	struct mpic *mpic;
-	struct device_node *np;
-
-	np = of_find_node_by_type(NULL, "open-pic");
-	if (np == NULL) {
-		printk(KERN_ERR "Could not find open-pic node\n");
-		return;
-	}
-
-	mpic = mpic_alloc(np, 0, MPIC_PRIMARY | MPIC_WANTS_RESET |
+	struct mpic *mpic = mpic_alloc(NULL, 0,
+	  MPIC_PRIMARY | MPIC_WANTS_RESET |
 	  MPIC_BIG_ENDIAN | MPIC_BROKEN_FRR_NIRQS | MPIC_SINGLE_DEST_CPU,
 	  0, 256, " OpenPIC  ");