board: atmel: 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.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
diff --git a/board/atmel/at91sam9263ek/at91sam9263ek.c b/board/atmel/at91sam9263ek/at91sam9263ek.c
index b37e9d3..9fa6893 100644
--- a/board/atmel/at91sam9263ek/at91sam9263ek.c
+++ b/board/atmel/at91sam9263ek/at91sam9263ek.c
@@ -160,7 +160,7 @@
 		dram_size += gd->bd->bi_dram[i].size;
 	nand_size = 0;
 	for (i = 0; i < CONFIG_SYS_MAX_NAND_DEVICE; i++)
-		nand_size += nand_info[i]->size;
+		nand_size += get_nand_dev_by_index(i)->size;
 #ifdef CONFIG_MTD_NOR_FLASH
 	flash_size = 0;
 	for (i = 0; i < CONFIG_SYS_MAX_FLASH_BANKS; i++)