mtd: ensure UBI is compiled when using fastmap

UBI must be enabled when using fastmap, reflect this is defconfigs.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
diff --git a/configs/colibri-imx6ull_defconfig b/configs/colibri-imx6ull_defconfig
index aa0ec63..055f247 100644
--- a/configs/colibri-imx6ull_defconfig
+++ b/configs/colibri-imx6ull_defconfig
@@ -64,6 +64,7 @@
 CONFIG_SYS_NAND_USE_FLASH_BBT=y
 CONFIG_NAND_MXS=y
 CONFIG_NAND_MXS_DT=y
+CONFIG_MTD_UBI=y
 CONFIG_MTD_UBI_FASTMAP=y
 CONFIG_PHYLIB=y
 CONFIG_PHY_MICREL=y