mtd: nand: Patch remaining places where nand_to_mtd() should be used

Some drivers are still directly accessing the chip->mtd field. Patch
them to use nand_to_mtd() instead.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
diff --git a/drivers/mtd/nand/nand_spl_simple.c b/drivers/mtd/nand/nand_spl_simple.c
index b023e00..60a7607 100644
--- a/drivers/mtd/nand/nand_spl_simple.c
+++ b/drivers/mtd/nand/nand_spl_simple.c
@@ -249,7 +249,7 @@
 	/*
 	 * Init board specific nand support
 	 */
-	mtd = &nand_chip.mtd;
+	mtd = nand_to_mtd(&nand_chip);
 	nand_chip.IO_ADDR_R = nand_chip.IO_ADDR_W =
 		(void  __iomem *)CONFIG_SYS_NAND_BASE;
 	board_nand_init(&nand_chip);