mtd: nand: mxs_nand: allow to enable BBT support

Add config option which allows to enable on flash bad block table
support. This has the same effect as when using the device tree
property "nand-on-flash-bbt" in Linux.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/drivers/mtd/nand/mxs_nand.c b/drivers/mtd/nand/mxs_nand.c
index 14d3210..2584608 100644
--- a/drivers/mtd/nand/mxs_nand.c
+++ b/drivers/mtd/nand/mxs_nand.c
@@ -1213,6 +1213,10 @@
 
 	memset(&fake_ecc_layout, 0, sizeof(fake_ecc_layout));
 
+#ifdef CONFIG_SYS_NAND_USE_FLASH_BBT
+	nand->bbt_options |= NAND_BBT_USE_FLASH | NAND_BBT_NO_OOB;
+#endif
+
 	nand_set_controller_data(nand, nand_info);
 	nand->options |= NAND_NO_SUBPAGE_WRITE;