powerpc/mpic: use of_property_read_bool

Use of_property_read_bool to check for the existence of a property.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e1,e2;
statement S2,S1;
@@
-       if (of_get_property(e1,e2,NULL))
+       if (of_property_read_bool(e1,e2))
        S1 else S2
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Scott Wood <oss@buserror.net>

arch/powerpc/sysdev/mpic.c

@@ -1249,7 +1249,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
 	/* Pick the physical address from the device tree if unspecified */
 	if (!phys_addr) {
 		/* Check if it is DCR-based */
-		if (of_get_property(node, "dcr-reg", NULL)) {
+		if (of_property_read_bool(node, "dcr-reg")) {
 			flags |= MPIC_USES_DCR;
 		} else {
 			struct resource r;