board: toradex: use get_nand_dev_by_index()

As part of preparation for nand DM conversion the new API has been
introduced to remove direct access to nand_info array. So, use it here
instead of accessing to nand_info array directly.

Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
diff --git a/board/toradex/colibri_t20/colibri_t20.c b/board/toradex/colibri_t20/colibri_t20.c
index 7d574fb..71b8fd3 100644
--- a/board/toradex/colibri_t20/colibri_t20.c
+++ b/board/toradex/colibri_t20/colibri_t20.c
@@ -69,7 +69,7 @@
 {
 	printf("Model: Toradex Colibri T20 %dMB V%s\n",
 	       (gd->ram_size == 0x10000000) ? 256 : 512,
-	       (nand_info[0]->erasesize >> 10 == 512) ?
+	       (get_nand_dev_by_index(0)->erasesize >> 10 == 512) ?
 	       ((gd->ram_size == 0x10000000) ? "1.1B" : "1.1C") : "1.2A");
 
 	return 0;