[POWERPC] Constify & voidify get_property()

Now that get_property() returns a void *, there's no need to cast its
return value. Also, treat the return value as const, so we can
constify get_property later.

powerpc core changes.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/sysdev/mmio_nvram.c b/arch/powerpc/sysdev/mmio_nvram.c
index 615350d..ff23f5a 100644
--- a/arch/powerpc/sysdev/mmio_nvram.c
+++ b/arch/powerpc/sysdev/mmio_nvram.c
@@ -80,7 +80,7 @@
 int __init mmio_nvram_init(void)
 {
 	struct device_node *nvram_node;
-	unsigned long *buffer;
+	const unsigned long *buffer;
 	int proplen;
 	unsigned long nvram_addr;
 	int ret;
@@ -91,7 +91,7 @@
 		goto out;
 
 	ret = -EIO;
-	buffer = (unsigned long *)get_property(nvram_node, "reg", &proplen);
+	buffer = get_property(nvram_node, "reg", &proplen);
 	if (proplen != 2*sizeof(unsigned long))
 		goto out;