[POWERPC] video & agp: 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-specific video & agp driver changes.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/drivers/video/riva/fbdev.c b/drivers/video/riva/fbdev.c
index 2788655..6a30c0c 100644
--- a/drivers/video/riva/fbdev.c
+++ b/drivers/video/riva/fbdev.c
@@ -1816,14 +1816,13 @@
 	NVTRACE_ENTER();
 	dp = pci_device_to_OF_node(pd);
 	for (; dp != NULL; dp = dp->child) {
-		disptype = (unsigned char *)get_property(dp, "display-type", NULL);
+		disptype = get_property(dp, "display-type", NULL);
 		if (disptype == NULL)
 			continue;
 		if (strncmp(disptype, "LCD", 3) != 0)
 			continue;
 		for (i = 0; propnames[i] != NULL; ++i) {
-			pedid = (unsigned char *)
-				get_property(dp, propnames[i], NULL);
+			pedid = get_property(dp, propnames[i], NULL);
 			if (pedid != NULL) {
 				par->EDID = pedid;
 				NVTRACE("LCD found.\n");