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_t20_defconfig b/configs/colibri_t20_defconfig
index c5b28bc..02fdc1e 100644
--- a/configs/colibri_t20_defconfig
+++ b/configs/colibri_t20_defconfig
@@ -45,6 +45,7 @@
 CONFIG_MTD=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_DM_MTD=y
+CONFIG_MTD_UBI=y
 CONFIG_MTD_UBI_FASTMAP=y
 CONFIG_DM_PMIC=y
 CONFIG_DM_REGULATOR=y