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/sama5d4ek/sama5d4ek.c b/board/atmel/sama5d4ek/sama5d4ek.c
index b2e7979..ba79746 100644
--- a/board/atmel/sama5d4ek/sama5d4ek.c
+++ b/board/atmel/sama5d4ek/sama5d4ek.c
@@ -153,7 +153,7 @@
 	nand_size = 0;
 #ifdef CONFIG_NAND_ATMEL
 	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;
 #endif
 	lcd_printf("%ld MB SDRAM, %ld MB NAND\n",
 		   dram_size >> 20, nand_size >> 20);