mtd: plat-ram: add const quilifiers

Be a bit stricter and add few more 'const' qualifiers.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/maps/plat-ram.c b/drivers/mtd/maps/plat-ram.c
index 2de66b0..71fdda2 100644
--- a/drivers/mtd/maps/plat-ram.c
+++ b/drivers/mtd/maps/plat-ram.c
@@ -199,7 +199,7 @@
 	 * supplied by the platform_data struct */
 
 	if (pdata->map_probes) {
-		const char **map_probes = pdata->map_probes;
+		const char * const *map_probes = pdata->map_probes;
 
 		for ( ; !info->mtd && *map_probes; map_probes++)
 			info->mtd = do_map_probe(*map_probes , &info->map);