[POWERPC] Fix device_is_compatible() const warning

Fix a const'ification related warning with device_is_compatible()
and friends related to get_property() not properly having const
on it's input device node argument.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 865b964..bdb412d 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1014,7 +1014,7 @@
 /** Checks if the given "compat" string matches one of the strings in
  * the device's "compatible" property
  */
-int device_is_compatible(struct device_node *device, const char *compat)
+int device_is_compatible(const struct device_node *device, const char *compat)
 {
 	const char* cp;
 	int cplen, l;
@@ -1491,7 +1491,8 @@
 __initcall(prom_reconfig_setup);
 #endif
 
-struct property *of_find_property(struct device_node *np, const char *name,
+struct property *of_find_property(const struct device_node *np,
+				  const char *name,
 				  int *lenp)
 {
 	struct property *pp;
@@ -1512,7 +1513,8 @@
  * Find a property with a given name for a given node
  * and return the value.
  */
-const void *get_property(struct device_node *np, const char *name, int *lenp)
+const void *get_property(const struct device_node *np, const char *name,
+			 int *lenp)
 {
 	struct property *pp = of_find_property(np,name,lenp);
 	return pp ? pp->value : NULL;