mtd: maps: add const qualifiers

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/gpio-addr-flash.c b/drivers/mtd/maps/gpio-addr-flash.c
index 7b643de..5ede282 100644
--- a/drivers/mtd/maps/gpio-addr-flash.c
+++ b/drivers/mtd/maps/gpio-addr-flash.c
@@ -157,7 +157,8 @@
 	memcpy_toio(map->virt + (to % state->win_size), from, len);
 }
 
-static const char *part_probe_types[] = { "cmdlinepart", "RedBoot", NULL };
+static const char * const part_probe_types[] = {
+	"cmdlinepart", "RedBoot", NULL };
 
 /**
  * gpio_flash_probe() - setup a mapping for a GPIO assisted flash