mtd: nand: mxs_nand: introduce SPL specific init

In preparation to convert the driver to use NAND self init
provide a new minimal init for SPL builds. As a side effect
this also reduces size of SPL by about 4KiB.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/drivers/mtd/nand/mxs_nand_spl.c b/drivers/mtd/nand/mxs_nand_spl.c
index 3e8b35f..47857a8 100644
--- a/drivers/mtd/nand/mxs_nand_spl.c
+++ b/drivers/mtd/nand/mxs_nand_spl.c
@@ -6,6 +6,7 @@
 #include <common.h>
 #include <nand.h>
 #include <malloc.h>
+#include "mxs_nand.h"
 
 static struct mtd_info *mtd;
 static struct nand_chip nand_chip;
@@ -145,7 +146,7 @@
 		return 0;
 
 	/* init mxs nand driver */
-	board_nand_init(&nand_chip);
+	mxs_nand_init_spl(&nand_chip);
 	mtd = nand_to_mtd(&nand_chip);
 	/* set mtd functions */
 	nand_chip.cmdfunc = mxs_nand_command;